An auction is the process of buying and selling goods or services by inviting competing bids from a number of participants.  Competing participants in an auction may or may not know the identities or actions of other competitors.  Forward auctions involve buyers submitting competing bids, with the price typically increasing during the auction.  Reverse auctions involve sellers submitting competing bids, with the bids usually decreasing during the auction.  Online reverse auctions are a common tool for procurement practitioners seeking to harness competitive tension for relatively undifferentiated categories.  Some platforms allow the buyer to evaluate bids against a variety of criteria as well as price, and bidders may have visibility on the actual prices bid, or simply the ranking of their offer in terms of competitiveness against the other bids received by the buyer.  See also Auction, Dutch.