Music industry watchers are buzzing about Turntable.fm, a service that cleverly combines music streaming, social media, and gaming. Even Lady Gaga and Kanye West are on board. So what exactly is Turntable.fm? Here, a brief guide:

What's this site all about?

It's an online startup that "merges" free music streaming and chatrooms into "a type of game" that's accessed through Facebook, says Leslie Horn at PC Mag. Users have to be invited to the site, where they can create rooms where they become virtual DJs, playing songs — either through streaming or tracks uploaded from their own computers — for other members. A chatroom sidebar allows participants to rate the song as either "awesome" or "lame," which scores the DJ points. In other words, says Peter Kafka at All Things D, you share your favorite songs with a group audience — and you can do it "in real time, for free."

How popular is it?

Since its launch earlier this summer, Turntable.fm has accrued over 300,000 users, says Brenna Ehrlich at Mashable. It's also benefiting from good word of mouth. Corey Tate at Spacelab says it's the "go-to site right now," while Liza Eckert at Death + Taxes says those unaware of the site are "uninitiated" and "living under a rock." The most telling sign that Turntable.fm is about to break out: Someone already launched "a complete knock-off" of the site's concept, says Eliot Van Buskirk at Billboard. A site called Rolling.fm does everything the "original service does," indicating the start of an "explosion of group listening services" like Turntable.fm.

Is it legal?

How could a site provide music for free and do it legally? According to Turntable.fm's founder, the service is under the same protection that lets Pandora operate, says Kafka. There's a limit on the amount of times a song can be played, users can't see what song is coming next, and, unlike radio, it's interactive. That may seem like "murky legal territory," says Eckert, but the site made big strides last month by striking deals with both the American Society of Composers, Authors, and Publishers (ASCAP) and Broadcast Music, Inc. (BMI). That means those industry groups can collect royalties for songwriters. Still, Turntable.fm has no deals with record labels.

What's next for Turntable.fm?

The site is "gaining legitimacy day by day," says Brenda Ehrlich at Mashable. With Kanye West and Lady Gaga contributing to this week's $7.5 million financing round, the startup's value is now at about $37.5 million. But Kanye and Gaga's involvement could be worth far more than that. What better way to get the music industry on board, says Allyson Shontell at Business Insider, than "getting influential artists" as investors?

Sources: All Things D, Billboard, Business Insider, Death + Taxes (2), Mashable (2), PC Mag, Spacelab