First-price auctions are a type of auction in which the winning bidder pays the exact amount of their bid. In a first-price auction, the seller sets a reserve price, which is the minimum price at which they are willing to sell the item or service being auctioned. Bidders then place their bids, and the highest bidder wins the auction and pays the amount of their bid. First-price auctions are different from second-price auctions, in which the winning bidder only pays a small increment above the second-highest bid, rather than the full amount of their own bid. First-price auctions are commonly used in the online advertising industry, where they are often used to determine the winning bid for ad impressions in real-time auctions.