Auctions are a common way to set prices in many markets. Buyers compete by submitting bids to a seller, who then decides how to allocate the supply. There are different pricing rules, like each successful bidder paying their bid price or all paying the same price. Auctions have been used for a long time and are a simple way to determine prices without middlemen. They are important in economic theory and are often used in experiments to test economic theories. Auctions are good for studying game theory because they have clear rules that affect how bidders behave. Bidders' private information plays a big role in how auctions work.