Who

WHO shows the people currently in the game.  Some people may choose to remain unseen and won't appear on the WHO
WHO without any arguments shows all of the (visible) people currently playing.

With arguments, WHO can show players of levels.
For example:

who 10          lists all players of level 10 or above
who 15 20       lists all players between level 15 and 20
 

Syntax: who <level-range>