What is the difference between an alias and a tag in APNS? What is the difference between an alias and a tag in apns?

What is the difference between an alias and a tag in APNS? What is the difference between an alias and a tag in apns?

Alias: an alias is used to identify a user who has installed an application. Each user can only have one alias, which is used to push information to the user,

Although the system does not limit that one alias can only identify one user, In order to uniquely identify a user based on the alias, it is best to have one alias corresponding to one user;