sudo is not only to sudo (execute files as another user)

If you want to execute a command with root privileges, you normally use the command "sudo". But of course you can execute a command also as any other user. E.g. I need to execute some script for my backup as user "backuppc". then I just type:

sudo -u backuppc /usr/local/backuppc/bin/BackupPC_serverMesg status info

Instead of the username (backuppc) one can also use the user id (uid).