The referral link is a form of "invite a friend", that rewards you for making the site popular.
You can send your referral link to someone, instead of the standard avpvm.com link. The referral link will point them to the first page of the site. Whenever they visit the site by using your link, you will get money.

Your link is located here:
Example:

http://www.avpvm.com//index.php?refer=YOURNAME

You will get some money just for them using that link and registering directly from that link.

Once they register, you benefit from them posting. Once they reach a certain rank, you get a kickback of money.

So the more active the person you recruited is, the richer you become!