who is one of basic Unix commands, which allows you to quickly see who else is logged in.
who – default behaviour
When you run who without any parameters, it returns you a list of users on your Unix system, along with terminals they're using, the time of the start for each session, and the hostnames where these users are logged in from.
bash-2.03# who ann pts/2 Jan 16 08:36 (linuxws-1) greys pts/4 Jan 17 10:37 (linuxserver)
who am i
When you just want to confirm how many login sessions you have running on the system, you need to use a special form of the who command:
bash-2.03# who greys pts/4 Jan 17 10:37 (linuxserver)
Because my username is greys, I can only see my own sessions.