The security of this method depends on the fact that, while it's easy to go from your clear password to the encrypted version, the reverse is very hard. Thus, even if someone can see the encrypted version of your password, they can't use your account. Once you have successfully logged in, you get all the privileges associated with the individual account you are using. You may also be recognized as part of a group . A group is a named collection of users set up by the system administrator.
Groups can have privileges independently of their members' privileges.
A user can be a member of multiple groups. Your account entry also contains your home directory , the place in the Unix file system where your personal files will live. Finally, your account entry also sets your shell , the command interpreter that login will start up to accept your commmands.