The site invites you to search for an artist and presents you with a list of tracks found that you can either listen to on the site or download. The site doesn’t host or distribute tracks, it is a search engine, but it’s not hard to see why the record labels whince when piracy is made this easy by a site. Moreover, I suspect that the sites that are hosting the content are unwittingly assisting the piracy rather than deliberately participating.
Whilst it is not as slick as Seeqpod [no saved playlists, video or discover features] it is astonishingly fast and has no user sign-up requirement. Use with care.