Help: How does the Invite system work?

How does the Invite system work?

This is great fun (and the piece of code of which we are most proud :-) ). If you have a crush on someone, but don't want to tell them just yet, use the invite system. This invites them to join Romance.ucam.org - they will receive an e-mail saying that somebody (they will not be told who...) has invited them to join. It is exactly like sending a Valentine's card, but the recipient has a chance to respond to the anonymous sender by sending you messages on the site. The way that this works is that an anonymous communication channel is set up between you when they reply - not even your Romance.ucam.org nickname is revealed. [show maths]. You can include a short message with the invitation, if you like. Good luck, and enjoy....
N.B. Your invitee must have a '@cam.ac.uk' email address. For more information, click Invite.