referrals

Under general information in my user profile, something says, Referrals: 0. What does that mean?

So...My Administrator...I was wondering if there were any prizes or rewards available. :P But since there probably aren't, what do people think would be cool prizes for say, refering 100 new users? PS: http://forum.esforces.com/faq.php?faq=vb_board_usage#faq_new_faq_item <---down the very bottom