Auctions

English Auctions: buyers keep raising bid until no one raises in higher.
Dutch Auctions: Auctioneer starts at a very high price and continues to lower price until a buyer announces a bid at that price.
Sealed Auction: buyers put bid in an envelope. At designed time, envelopes are opened and the buyer submitting the highest bid wins at that price
Vickrey Auction: Like sealed bid auction, but highest bidder only has to pay the 2nd highest amount bid.