Apple ID considered as an all-in-one account that allows the user to login into different online systems.
It is a personal account that gives you access to Apple Services such as Apple Store, iCloud, iTunes Store, iMessage, FaceTime, and the Apple Online Store. It allows you to integrate the email address and the password to sign in, and also it provides the contact, security and payment details which you can use it for Apple Services.
You can use your Apple ID at any time when you setup a new device, or if you buy something, or utilize the Apple service.