Today's traders need low spread, deep liquidity, price transparency, anonymity, low slip and low latency. It is not easy to meet these needs, especially for each trader has different needs in price and transaction execution. STP straight through trading mode enables the dealer to gather all its liquidity providers, set up an order book with all the quotations, and then provide its customers with the best purchase and sale prices. The high volume of transactions pooled by all the dealers' customers can encourage price competition among liquidity providers and provide better leverage to demand better execution. In the first mock exam, liquidity can be effectively flowing between price providers and price receivers, so as to meet the needs of customers and provide the best trading environment for modern traders.