An Apple ID gives you access to the iTunes Store, App Store, iBooks Store, iCloud, FaceTime, and other Apple services. It consists of an email address (for example, firstname.lastname@example.org) and a password. For more information about Apple ID, or to create one, go to the Apple ID acccount website.
All of your purchases are tied to your Apple ID, and can’t be transferred to another Apple ID. If you make purchases on your iPad, iPhone, or another Mac, always sign in using the same Apple ID so you can see all of your store purchases on this Mac and download any available updates.
It’s recommended that you use the same Apple ID for all Apple services, including the iTunes Store, App Store, and iBooks Store. However, if you already use different Apple IDs for different services, you can continue to do so. For more information, see the iTunes Support page and the “Use different Apple IDs for iCloud and iTunes” section on the Sign in with your Apple ID page.