referrals

[mono]

I feel so ignorant in my asking, but on everyone's profiles I have noticed a specific part for 'referrals.' What are the referrals, and what do the numbers indicate?
Thank you, anyone, in advance.

[Logos]

This topic (http://www.online-literature.com/forums/showthread.php?t=2455) was asking this question as well.

[mono]

Ah, thank you, Logos. I have 'referred' people without knowing it, one of whom has joined, but I guess I never saw the link in my profile.
Thanks again.