Non-Login Use of Passwords
Entering a single password to log into a system and subsequently having access to all the user's resources is, in most environments, a reasonable mix of security and convenience. It's not the only way to do it. Some systems permit password protection on individual files. A user could specially protect certain files so that someone learning the user's login password still couldn't get at those files.
Similarly, applications could require their own authentication of a user before permitting access to certain databases (even after the user has logged in).