classifieds auction option

I've noticed that when you start a listing to sell an item it list auction as one of the options. I've never noticed anybody selling by the auction method. How does the auction work here on SS? Do you just keep track of the bids yourself or is there some sort of automated system that keeps track of bids?

I have seen a couple things sold on here in auction form, but not alot. and I never had money for any of it.

How it work I dont know.