How should user lock his terminal in UNIX system?

Sometimes user have to be away from his terminal, but don’t want to logout because  a job is running in the background. This is done by ‘lock’ command. It requires you to enter a password when you decide to lock it.
Syntax—
     <prompt> lock
Output—
     Password : ******
     Re-enter password : ******
     Terminal locked by Ram 0 minutes ago