An Apple ID consists of an email address (for example, firstname.lastname@example.org) and a password. In some locations, you can use a phone number instead of an email address. See the Apple Support article Use your mobile phone number as your Apple ID.
Your Apple ID gives you access to download items from the iTunes Store, use Genius, or subscribe to iCloud Music Library and other Apple services. It’s recommended that you use the same Apple ID for all Apple services.
Your purchases are tied to your Apple ID, and can’t be transferred to another Apple ID. If you make purchases on your iPhone, iPad, or another computer, always sign in using the same Apple ID so you can see all of your store purchases on this computer and download any available updates.