Make brute here: http://mybrute.com
Then you'll see how pupil looks like.
A pupil is a player who joins the game by clicking your brute link, you can find this link in your cell.
Anyone who creates a new brute and starts fighting your brute is considered your pupil. Whenever one of your pupils gains a level you will gain 1 XP.
Your pupils will see you as their Master, just like you will see the person that referred you as your master.