There are several types of auctions, each with its own rules and format. The most common is the English auction, where bidding starts low and increases as participants openly place higher bids. The highest bidder wins the item. In contrast, a Dutch auction begins with a high price that gradually decreases until someone accepts the current price.

Another type is the sealed-bid auction, where all bidders submit their offers secretly, and the highest bidder wins. A special form of this is the Vickrey auction, where the highest bidder still wins but pays the second-highest bid amount. Each type of auction is suited to different situations and goals.