You need an Apple ID to download items from the iTunes Store, use Genius, or subscribe to iCloud Music Library. It consists of an email address (for example, firstname.lastname@example.org) and a password.
Note: In some locations, you can use a phone number instead of an email address as your Apple ID. See the Apple Support article Use your mobile phone number as your Apple ID.
If you’ve purchased items from the Apple website or used iCloud Photos in the Photos app, or if you have an iCloud account, then you have an Apple ID. If you don’t have one, you can set one up using iTunes.