In CEX, there is a very important role, is known as a market maker (marketmakers), with each business users do counterparties, help you to complete the transaction. For trading in BTC/USDT, for example, when you buy the BTC, is essentially you with an expectation of price comparison, sold a certain amount of USDT market maker, at the same time from his hand in return for the corresponding number of BTC. Traditional market maker will be in the order book system stratification, active deity tho...