An auction is the process of selling or buying goods or services by inviting competing bids from multiple service providers or vendors. The competing participants may or may not know the identities or actions of other competitors. Auctions can be of two types: forward auctions and reverse auctions. While, in forward auctions, the bids increase during the auction, it decreases in the case of reverse auctions. Online reverse auctions are commonly used by procurement professionals seeking the best value deal.