Twitter has purchased Gnip. That's a sentence that might have looked totally alien to readers a decade ago. Today, at least one of those companies has become a household name. But what's Gnip, and why does Twitter want it so badly when it's actually been working with the company for years now?

The big play here is about user data. That shouldn't come as a surprise if you've been paying attention to other companies that have tried to monetize their customers. But for Twitter, the move is crucial, considering it hasn't quite figured out how to turn a profit yet.

For the uninitiated, Gnip acts as an intermediary between Twitter and companies (read: marketers) that want to know what social media users are talking about. Gnip's existing agreement with Twitter lets it sell access to the full, unfiltered "firehose" of tweets; Gnip also has access to the full, historical Twitter data archive going back about a month. Selling its data to Gnip and others earned Twitter some $70 million last year, or about 11 percent of its annual revenue.

Bringing Gnip in house eliminates a middleman and lets Twitter sell directly to advertisers and brand managers.

"Gnip has played a crucial role in collecting and digesting our public data and delivering the most essential tweets to partners," Twitter wrote in a blog post.

Selling data is just one of a number of bets Twitter's made to bolster its revenue. It's also exploring a future in live TV, for instance, and it's actively courted political campaigners to buy promoted tweets. But the fact that Twitter is expanding its commitment to selling user data suggests it still hasn't found the magic formula to push the company into the black.

One outstanding question has to do with Gnip's access to data from other social media companies. Its programming interfaces give customers insights on what users are doing on WordPress, Tumblr, Instagram and other major sites. Will Twitter, through its purchase of Gnip, get to peek at that data, too?

I've reached out to Twitter for a comment and will update if and when I hear back. Twitter declined to comment.