What are "referrals"?

[Immanuel]

I was looking at the statistics page in my User CP and noticed an item titled "Referrals" and it now has a one beside it. What is referrals? For a long time, I thought it meant the number of users that I had referred to the site, but since I can't think of any whom I have referred that doesn't make any sense.

Does, it mean I have been referred to the principal's office for a post I made? Did I piss someone off enough to run and tattle on me?

Can I find out who it was? Please!!! So I can try harder next time?

Immie