Authentication is basically used to find are you really the person who you claim to be with the help of login and password
Whereas Authorization is used to determine which level of permissions you have like to determine whether you have admin access or developer access
For example: If you want to access the database server
you should first know who is trying to access it
Then you should know what kind of access they have like do they have access to edit, create, update or delete
Auth can mean either, but is used more often as "User Auth" i.e. "User Authentication"