Auctions

Sellers (Forward) auctions
A forwards auction involves is a single seller and many potential buyers. Sellers list products at the lowest price which they are happy to accept. The seller has the option, but not the obligation, to sell below his asking price. Bids below the asking price will be recorded and displayed so that the seller can see what buyers are willing to pay. At the end of the auction, if the high bid is below the asking price, there is no winning bidder.
At no time during the auction can a seller raise his asking price, or lower the quantity offered. At no time during the auction can a buyer lower his bid, withdraw his bid, or reduce the quantity.

Buyers (Reverse) auctions
A reverse auction involves one buyer and many sellers. The buyer specifies what they want to purchase, and offers it to many suppliers. The process will usually produce the lowest possible price.