What is an apple id?

Question

Apple ID

Is apple id just email (or phone number)?
Or does something else serve as an identifier?
For example, for a VK page, in addition to email and phone number, the id of the VKontakte page also acts as an identifier.
That is, even if you change the email and phone number associated with the VK page, it will still have the same page id as one of the identifiers.
Is there something similar for apple id? Or is there only an email (or phone number) as an identifier?

Answer 1

In any case, there is. No one in their right mind uses login/email/whatever as a primary key. Another thing is that this identifier may not be publicly available, but can be used only for technical needs.