In Facebook (Meta) ads, “buying type” refers to the method by which you pay for, target and measure ads in your campaigns. Primarily, there are two options for buying type: Auction and Reservation (formerly known as Reach and Frequency). The Auction buying type is the default and most commonly used buying type for Facebook Ads. The Reservation buying type allows you to plan and book your campaigns in advance at a fixed cost, but has limited availability and options.