Regular exchanges are based on order book models. (Binance, Coinbase, Nasdaq, etc.…) In this order book model, buyers and sellers come together and place their orders. Buyers (Bidders) try to get in at the lowest price possible. Sellers try to sell at the highest price possible. For the sale to occur, the buyer and seller must converge and find a common ground that they agree upon. If no one can place their product at a fair price or there are not enough of a supply; that is where market makers come into play.