You’ve probably never heard of Pattie Sellers. But Warren Buffett has. And so have Sheryl Sandberg, Oprah Winfrey and Indra Nooyi.

It’s an enviable list, really.

They’re among the many who’ve joined Sellers at the Most Powerful Women summit. This year, from a slightly raised stage, she looks out once more across table upon table of some of the world’s most prominent female executives, artists and philanthropists. It’s the opening dinner of Fortune magazine’s annual summit on a surprisingly chilly October evening on the Southern California coastline. The 400-plus guests sit under a big, white tent on a cliff perched over the gray, choppy Pacific. Inside, the Ritz-Carlton has pulled off something that looks a lot like prom: purple sequined tablecloths and settings of pink roses illuminated by purple and pink floodlights.

It’s Fortune’s event, but it’s Sellers’s party. Every seat is filled. An additional 200-plus women on the invitation-only list were ready to hand over $5,500 for a three-day ticket. They just weren’t fast enough.

Sellers is the brains behind Fortune’s 50 Most Powerful Women rankings and the heart behind this annual summit. She has boyishly short brown hair and laughs like Julia Roberts, that kind of toothy, head-back guffaw.

When Fortune inaugurated the list in 1998, it was the first of the magazine’s famous tallies not based purely on statistics — revenue in the case of the Fortune 500 and survey results in the case of Most Admired Companies. Instead, this was a ranking based on the amorphous concept of “power.” And for 13 years, Sellers has been a key decider of who’s got it.

She’s well positioned to make such calls. Her cover stories for Fortune often delve into the biggest personalities of big business. On her blog, “Postcards,” she looks at the lives of super-achievers and the news they’re making that day. There, she posted the expletive-laced exclusive with Carol Bar tz after she was fired from Yahoo in September.

Sellers arrived at Fortune in 1984, two years after graduating from the University of Virginia. From early on, many of her stories gravitated toward an exploration of power.

The first of these was a profile of Liz Claiborne. “I was totally intimidated,” Sellers says. As she recalls, a cold and terse Claiborne made for a difficult interview. “At the time, there was a forced image that women projected to appear powerful. They couldn’t be completely natural if they were going to be seen as powerful. Their guard had to be up.”

Getting inside such fortresses turned into a career-defining pursuit.

“She is just unabashed in her hunt, her quest, for the perfect story,” says Sue Callaway, a co-founder of the Most Powerful Women enterprise and Sellers’s former editor who got many a knock from Sellers on her office door. “She was a rare writer who drove me crazy from just wanting that level of editing.”

In 1996 and 1997, Sellers reported two big cover stories on women for Fortune — “Women, Sex and Power” and “The Toughest Babe in Business.” And it was the success of these, at a publication that had focused heavily on the typical cast of male business characters, that helped inspire the annual women’s power list.

“Thirteen years ago at Fortune, there was a real struggle internally to effectively and appropriately cover women in business,” Callaway says. “The coverage for females in the corporate world had really been very sporadic, and it felt, some of it, like tokenism.”

The rankings

One way to give women a foothold in Fortune’s coverage was to start the list, which has become a standard cheat sheet for who’s who of women in business.

“I said, we have to rank them,” Sellers says, recounting a decisive meeting early on with then-No. 2 editor Rik Kirkland and Callaway. “It’s the only way that guys will read this thing, because guys are into stats and status and size and rank.”

What emerged was a process of gathering as much objective criteria as possible about these female moguls: how quickly a woman had ascended the ranks, how many career moves she’d made, her earning capacity, the number and nature of boards she sat on, the titles she had held, and her company’s heft in its industry and the broader economy. Ultimately, the rankings could never fully escape the subjective, but Sellers and Callaway were determined to get the concept of power as close as possible to quantifiable.

Today, rankings of women are pervasive. But at the time, it was a bold statement about women in business — and one that slammed right into the question: What is and isn’t sexist?

Initially, some women criticized the rankings as too male. Others saw the first Most Powerful Women cover as, well, too feminine. It showed then-Lucent executive Carly Fiorina curled up on a couch in a soft sweater and equally soft lighting.

“The internal debates raged again about whether we were defining our own brand of tokenism,” Callaway says. “And we decided, no. It was okay. It was okay to be a woman. That was the point of this measurement, and we would let her look feminine on the cover.”

Out of those struggles emerged the second biggest jewel in the Fortune crown. The conference got its start a year later in 1999. The multimillion-dollar franchise brings in money from sponsorships, advertising and tickets; next year, the ticket price will jump to $7,500 for three days.

That first year, about 200 women gathered at the Hudson Theatre in New York’s Times Square on a more expectedly cold October night. On the same day, it so happened, Martha Stewart Living Omnimedia went public. Sellers was on stage with Fiorina — who had gone from relatively unknown Lucent division chief to Fortune cover star to HP’s top executive — when Stewart came through the door.

“Martha walked in, in like this big furry coat,” Sellers recalls, “and I remember saying on stage, ‘Martha Stewart became a billionaire today.’ And it was just kind of a cool moment, you know?”

Over the years, there have been many others: Stewart taught a yoga class. Cyndi Lauper sang “Girls Just Wanna Have Fun” while standing atop a table where tech titan Meg Whitman was sitting. Nora Ephron pressed Nancy Pelosi on how it felt to be called “Madame Speaker.”

‘Love . . . Warren’

Back under the big tent at this year’s event, Sellers addresses the crowd with the effusive warmth of someone greeting old friends. This year she has co-chairs, Fortune’s Nina Easton and Stephanie Mehta, yet Sellers still offers the first brimming words of thanks and welcome.

“I think when she was younger, she was more shy,” says Lisa Clucas, the summit’s program director and a high-school friend of Sellers’s from Allentown, Pa. “But I’d say from her 20s on, she’s been very gregarious.”

Sellers has charmed devotees of the summit as resolutely as she has cultivated sources for her reporting, and they are often one and the same. Case in point? Buffett, the “Oracle of Omaha,” was a source for Sellers when she covered Coca-Cola. In time, he was reaching out to her with a five-by-seven-foot Colossal Gram: “Pattie . . . Happy 50th birthday to the most powerful woman of them all! Love . . .Warren.”

Only two men have snagged slots at the 2011 summit: Buffett, of course, and Lloyd Blankfein, chief executive of Goldman Sachs. They are seated at a table close to the makeshift stage. “I get invited to a lot of things,” Buffett says, “but this is the one I clear the calendar for.”

He has been distracted all night from his specially ordered hamburger as woman after woman leaves her plate of salmon to tap his shoulder and ask for a picture. Now, he’s the one waiting for Sellers. An event photographer has asked to shoot the two of them before the night is over, but Sellers won’t yet break away from other guests.

Here, everyone is in turn a star and star-struck. Take Tyra Banks. “It’s like, ‘Oh my gosh, I’m going to be in the same room as Meg Whitman?!’ ” she said. “ ‘Oh my gosh, I’m going to be in the same room as Indra Nooyi?!’ This is crazy.”

Inside the tent, the gala has ended. BlackBerry screens flicker on and float out toward the lawn and the suites beyond, and Buffett is still waiting. Sellers is chatting nearby with a small circle of women lingering in the opening night’s afterglow.

“She gets together women that no one has ever gotten together before,” Buffett says. “And she makes you feel good about it.”

That “feel good about it” part is key. These are exceptional women, yet inherent in that accolade can be the lonely reality of “exception.” Fewer than 4 percent of Fortune 500 companies have female CEOs, which gives you a sense of how rarely high-powered women find themselves together, let alone 400 under the same magenta-lit tent.

This event has the feel of a lean-to shelter — albeit a luxe one — for women traveling across the tundra of a male-dominated business world. For three days, they get to talk with other women there about the journey. Beneath it all, mostly unspoken, are the simple words: “Oh, good. You’re here, too.”

And who’s there — at the summit, as in the business world itself — is changing. Although it is still important to Fortune to keep the event elite and exclusive, offshoot programs such as the Most Powerful Women Entrepreneurs and the Fortune/U.S. State Department Global Women’s Mentoring Partnership have made the circle more youthful, more global and simply bigger.

Connecting the hyper-connected

At 51, Sellers has found her own, quiet seat among these changemakers. And through the years, the novelty of women’s power has given way to the question of how best to use it.

Sellers “probably exemplifies better than anybody the idea of using her power for good,” says Dina Powell, who helped launch the State Department partnership as an assistant secretary of state. “She’s also the person that is so humble and never takes credit for anything.”

Among the other things Sellers has never done: She has never married or had children. She has also never seen a woman hold the top editor position at the magazine where she has spent 27 years.

What she has done is find ways to connect women and to empower them in the process. These people are, on the surface, hyper-connected. Brimming Rolodexes. Stacks of business cards. Corporate entourages. E-mails and phone calls at all hours. And yet they board planes, drag luggage through airports, sit in board meetings, take calls from shareholders, and often feel — despite all the activity around them — “I do this alone.”

“Be first and be lonely,” said Ginni Rometty on stage at this year’s event. She was recently named IBM’s next chief executive, which will bring the number of Fortune 500 female CEOs to 18. High-powered men experience this, too. After all, Rometty was quoting outgoing IBM chief Sam Palmisano.

Even so, the grand irony is that these women often buck feminine stereotypes — say, demureness or domesticity — only to be labeled female everywhere they go. They’re asked, “What’s it like to be your company’s first female CEO?” Or, “Do you think our female customers will like this?” They become emblems of womanhood while, in many ways, living what is still culturally viewed as a man’s life.

“There was a point in my career that I thought, ‘If I don’t curse a lot when I’m talking to people, maybe I’m not a leader.’ Because it’s what I knew,” says Josette Sheeran, executive director of the U.N. World Food Program. “For women, I think the toughest thing is figuring out how to assert their authority in a way that’s true to themselves.”

The conference, then, has something of this at its heart. What Sellers, with Fortune, has created in this event is a place to be a woman and, for at least a time, not the woman. For three days, the voices of society that say they’re not like other women and the voices of the C-suite that say they’re not like other executives synergize. The conference’s spa treatments, beaded conference badges, pink flowers, tote bags — they seem frilly at first, but then perhaps that’s the point. This is, after all, the power set paraded around as “women in business.”

Sheryl Sandberg, the chief operating officer of Facebook, recounted to the New Yorker’s Ken Auletta how Sellers chastised her years ago for not wanting her public calendar to show she was attending the summit. Sellers’s advice: Own it. “This is not women getting together to talk about women’s issues,” Sellers says to me. “This is the most prominent women leaders around the world getting together to talk about the big issues of the day.”

Sandberg is not the only one to overcome reservations. “A lot of the women that we’ve featured over the years haven’t necessarily embraced being called out like that,” Callaway says. “They’re uncomfortable with the word ‘power.’ ”

Of course, many women have come to embrace it. And over time, some have petitioned aggressively to be included in the rankings.

“We’ve had women refuse to come to the summit because they’re not on the list,” Sellers says, “which I always find really annoying.”

Sandberg is in attendance again this year, and she alternates roles on stage between interviewer of author and activist Somaly Mam and as Sellers’s interviewee. The stage, it should be noted, is a slightly raised platform in a room of black swivel chairs. Women are interviewed, only to descend back into the audience. It is a fluid, communal style.

Hovering in the green room’s doorway after the interview, Sandberg says Sellers “really helped create a community of women in business who can support each other. She’s kept that issue on the forefront. And, Sandberg adds, “she’s always made it about business, not gender.”

What it’s also about, in a way, is authenticity. Does Sellers define herself as a feminist?

“No,” she says. “It’s a little bit like asking me if I define myself as a human being.”

‘And that’s power’

It is Wednesday, the final day of the summit, and by noon, these women will be waiting outside the Ritz for black town cars to whisk them off to the airport for business-class flights across the country and the globe.

Sellers is in glasses, pants and flat shoes. You can almost see the magic dust of recent days wearing off. Mehta and Sellers and I sit around a coffee table, and we talk as the final speakers walk in and out, sit for makeup and have microphones threaded down their dresses.

Do they ever see a day, or even want to see a day, when there’s no need for a women’s event? There’s always going to be a need, Mehta says.

“It will never get to that point,” Sellers bluntly says. “We will never have anything near equality in — or parity, parity’s the better word — parity at the top of corporate America. Not because of glass ceilings, not because of any kind of discrimination, but because women make different choices. And have more choices. And are allowed to do other, are permitted to do other, things. And that’s power.”

So you don’t think 50 percent of Fortune 500 chief executives will ever be women?

I expect a rosy answer, or at least a dodging one, from Sellers, the woman who came up with the list, and the one who for three days now has been on stage motivating others to bring up the next generation of leaders.

“I don’t think it will ever, ever, ever change. Like, centuries from now, I don’t think it’ll ever change. And I think there’ll always be a place for women getting together. I think that’s okay,” Sellers says. Her voice goes up on the okay, not down. And again: “It’s okay.”

This is why people call Sellers authentic. But what is the mission, then, of this high-octane powwow?

“Listen, you know, Fortune has its business goals. This is a brand builder, this is a profitmaker, all that. For me personally, this is about bringing really interesting women together and nurturing their connections, and seeing these women — I mean, this sounds so hokey, but I so believe it, I so believe it — seeing these women use their power beyond their job descriptions.”

And that, ultimately, comes back to connection and, as Sellers said, choice. For the women who’ve made choices along the way that turned them into high-powered chief executives and athletes and media moguls, the journey is often lonely, the tundra at times barren and unforgiving. What they’re looking for — as what everyone in one way or another perhaps is looking for — is connection. A way to pass along the momentum that comes from striving toward something, from pursuing a passion.

That goes, too, for Sellers: “My favorite thing to do, more than anything, is connect people.” She says this, stretching out the word f-av-or-ite.

“You hear the passion in her voice,” Mehta says. “I mean, this is a calling.”

“It really is,” Sellers says, nodding.

“You hear people talk about how they’re called to missions in a very spiritual way. And I don’t say that in a hokey way,” Mehta adds. “I really mean it that for Pattie, this is something that’s deeply ingrained in her soul.”

There’s a hint of silence, like something clicked between them. It lingers into Sellers’s response. “Thank you.”