FairPlay
FairPlay is a digital rights management (DRM) technology created by Apple Inc., based on technology created by the company Veridisc. FairPlay is built into the QuickTime multimedia software and used by the iPhone, iPod, iPad, Apple TV, iTunes, and iTunes Store and the App Store. Formerly, all songs in the iTunes Store were encoded with FairPlay. Apple later started offering a selection of songs that, after an additional 50 cents is paid per song, could be downloaded FairPlay-free. Currently, in the US, Apple does not sell songs with FairPlay encryption. FairPlay digitally encrypts AAC audio files and prevents users from playing these files on unauthorized computers.
Read more about Fairplay.