A user identifier ( engl. user identifier UID) identifies at a computer clearly a user or a ( associated with the user ) account. Typically, this user is a natural person, more rarely, a group of natural persons.
The User Authentication is requested whenever you log in to the computer. The application will remain active until you close the session. Logging out may, for example, timeout, are automatically enforced.
Under POSIX-compliant operating systems, the command displays information about one's identity from id: user name, user ID (UID ), name of the primary user group number of the primary user group ( GID)