Visitors to dozens of major websites on Wednesday are seeing a special message about the future of the Internet — part of a broad campaign by the companies to stop what they say is a threat to the Web as most consumers know it. Among the participants? Some of the biggest names on the Web, including Facebook, Google, reddit, Twitter and Spotify.

In dispute are a set of federal regulations that bans Internet providers from slowing down, blocking or charging websites extra fees while treating other sites differently. The Federal Communications Commission is weighing how to repeal those so-called net neutrality rules in a move that's expected to benefit Internet providers such as Verizon and AT&T.

Tech trade groups and activist organizations, such as the Internet Association and Fight for the Future, argue that repealing the FCC's net neutrality rules would give Internet service providers (ISPs) too much power to determine what consumers can and can't see online, and for what price. So they've partnered not only with the likes of Google and Facebook but also some of the world's other top online destinations — including Airbnb and Netflix — to oppose the proposed repeal. Here's everything you should know about Wednesday's “day of action.”

What are we seeing on these websites?

Many of the participating businesses are publishing blog posts, adding a banner to their homepages or even tweaking their user interfaces to make it impossible to browse those sites without learning about the issue of net neutrality. Some, like reddit, have created a slow-loading pop-up message to show what a world without the FCC regulations could look like.

Others, such as Netflix, have placed a banner at the top of their homepages drawing attention to the issue.

Even Pornhub, one of the Internet's most popular porn sites and the 18th-largest website in the country, is on board.

So what is net neutrality?

Net neutrality is a principle about fairness on the Internet. It holds that no ISP should be able to unfairly manipulate your Internet usage or your experience of the Web, particularly in ways that harm other businesses. Proponents of the FCC's net neutrality rules, which were passed in 2015, say strong regulations are necessary to prevent ISPs from artificially directing customers to sites and applications they control or with whom they share special business relationships. Opponents say the rules are overly burdensome and that softening the rules would help them upgrade their networks.

The rules also ban Internet providers from extracting payments from websites as a condition of delivering their content to consumers' screens. The rules apply equally to wired and wireless provider, and also allow the FCC to investigate carrier practices that it deems a potential threat to competition.

The FCC wants to repeal its own rules that were passed two years ago?

That's correct. When President Trump was inaugurated, the FCC passed from Democratic control to Republican. Now, with a 2-1 majority, the Republican FCC is seeking to roll back the net neutrality regulations.

Why do Internet providers oppose the FCC rules?

Not all Internet providers are against the rules. For instance, some smaller providers support the regulations.

“Internet providers should not be able to charge content creators — like Netflix, Hulu or CNET — more money to stream their service, or have the ability to block others entirely,” said Dane Jasper, chief executive of the California-based Internet provider Sonic.

But more broadly, the industry has argued that the net neutrality rules prevent it from finding new ways to make money. As many Internet providers are looking to diversify their revenue by going head-to-head with Google and Facebook's advertising prowess, it's no longer enough to simply provide an on-ramp to the Internet, analysts say. Increasingly, ISPs such as Verizon are buying up content companies like AOL and Yahoo, while others, such as AT&T, are moving into television programming.

The net neutrality rules, they say, inhibit the development of new business models that let them adapt to the market. And they argue that the regulation causes them to spend less money upgrading their networks to be faster and more reliable.

How are Internet providers responding to the day of action?

Some industry-backed groups have bought advertising space in publications such as the Verge, Axios and Recode to promote their views.

One such group, Broadband for America, says the FCC rules should be replaced by congressional legislation mandating net neutrality. Other ISPs are expected to respond on social media. AT&T published a blog post Tuesday explaining why it was actually on the side of the demonstrators, arguing that it has always been for an open Internet. (This has been disputed by others, who say that the blog post is filled with "alternative history.")

USTelecom, an industry association, said that while it opposes the FCC's implementation of net neutrality, it supports the concept in principle. “ISPs support net neutrality — no blocking, throttling or unfair prioritization — they just don’t support Title II,” said Amy Schatz, a spokeswoman for USTelecom.

What is “Title II”? 

Consumer advocates say that Title II of the Communications Act is the only thing that makes the FCC's rules enforceable against Internet providers. Title II is the same law that the FCC uses to regulate traditional telephone companies; by deciding in 2015 to regulate ISPs using Title II, the FCC put Internet providers under some of the same obligations as phone companies.

The decision was highly controversial, analysts say, because ISPs feared it could allow the FCC to directly regulate the price of Internet access someday. While that day hasn't arrived, that hasn't stopped groups like USTelecom from filing a lawsuit to block the net neutrality rules. There's a possibility that suit may reach the U.S. Supreme Court, but the FCC has a chance before then to repeal the net neutrality rules.

What happens next? 

The FCC is accepting public comments on its net neutrality repeal proposal here, and will be doing so until mid-August. Then, the agency's commissioners will develop a final draft and vote on it, perhaps later this year or even beyond. The decision becomes official once it makes it into the Federal Register — though supporters of the regulation are widely expected to file their own lawsuit challenging the repeal should it go through.

Democrats are hoping to turn net neutrality into a campaign issue. But because the center of gravity now lies at the FCC and in the courts, not Congress, the implications for individual lawmakers may be relatively few. That could change, however, if Congress moves more actively to grapple with a net neutrality bill.