iCloud: Apple ID
The email address you use to access many Apple resources, such as the Apple Online Store, the iTunes Store, the App Store, the Mac App Store, and also iCloud features. If you’ve purchased products from any online Apple locations, or if you’ve turned on iCloud on any devices with iOS 5 or later installed, then you have an Apple ID.
If you already have an Apple ID, you should use the same email and password to set up iCloud on each of your iOS devices and computers.
You can find out which Apple ID you use with iCloud in these places:
On your iOS device, tap Settings > iCloud.
On your Mac, choose Apple Menu > System Preferences, then click iCloud.
On your Windows computer, if you have Windows 8, move the pointer to the upper-right corner of the screen to show the Charms bar, click the Search charm, then click iCloud Control Panel on the left. If you have Windows 7 or Windows Vista, choose Start menu > All Programs > iCloud > iCloud.
For more information about your Apple ID, visit the iCloud Support website.