Norton Ghost 15.0 - Backing up computer with mulitple user accounts

Does Ghost work at the computer level or individual user account level?  Meaning if the computer has user accounts for User1, User2, and User3, and I setup a backup while logged on as User1 to backup"My Documents", will Ghost backup only "My Documents" for User1 only or will it backup "My Documents" for all three users?  I guess another way to ask the question is does each user have to define their own backup?

 

Thanks,

David