Apple ID is an authentication system launched by Apple for its products, such as iWork, iTunes Store and Apple Store. As a fully functional account, Apple ID allows users to access various resources of Apple.
Because Apple ID can be used for a variety of products and services provided by Apple, it can also be called Apple account, MobileMe account, Mac account, iTunes Store account and iChat account.
The Apple ID can be used as login information for all Apple-related operations, including using iCloud to store content, downloading applications from the App Store, and purchasing songs, movies and TV programs from the iTunes Store.