Hello Hampmarj,
Thanks for using Apple Support Communities! We understand you are looking for some information regarding changing your Apple ID and your Apple ID notification email address. We are happy to provide some information on this.
Your notification email address is the email address that is separate from your Apple ID that we use to send you important account and security related information. An example would be if you forget your Apple ID password and need to have a verification code sent to you to reset your password, we would use your notification email address to send that to.
You can read more about the different email address we use with your Apple ID as well as the process to change your Apple ID below:
About your Apple ID email addresses
Change your Apple ID
We hope this helps.
Cheers.