Everything you need to know about Apple's iTunes, including iTunes desktop software on Windows and Mac, iTunes Store on iPhone, iPod touch, and iPad, and iTunes in the Cloud on iCloud
iTunes started off as Apple's desktop music player for Mac but has since become so much -- perhaps too much! -- more. iTunes on the desktop now runs on Mac and Windows, and in addition to playing your music, TV shows, Movies, podcasts, and more, also manages and syncs all of that, as well as apps and games, to your iOS devices via USB. The iTunes Store, which on the desktop includes the App Store and the iBookstore, is where you buy all your content. And if you're using iCloud, it's where you re-download iTunes in the Cloud, and manage iTunes Match.
Apple is expected to update the desktop version of iTunes to iTunes 11 sometime this month.