Whats a referral?

I just looked on FAQ and it says you must have a link to this site and somebody has used it and joined so you get some kind of bonus points or something ? Sorry, don't really know, just trying to help !
Sorry I don't know the answer, but I'd surely like to. How do you even know you've got a referral? Is it different to a 'reputation' thingy? And what's the significance of it all?
It just means people are joining based on your commentary. No major significance - just that your friends are coming :D