It's just a computer with a tv card attached to an HDTV.
No, it's a super-sized iPad. You won't watch channels any more, you'll watch apps. Some apps will be for regular TV channels (eg. NBC, ESPN), some will be for specific shows, some will be for shows you can't get on regular TV (vintage, foreign, etc.), some will be for internet video services like YouTube, some will access your PC's media libraries, and some will have nothing to do with video content (games, email, web, etc.). It will all be controlled by voice (eg. Siri) with iPad, iPod, or iPhone remotes. There will, of course, be an Android version, but it will be all over the place in terms of quality and app completeness, as different set manufacturers try to differentiate from each other.