U-based margin contract/currency based margin contract; Perpetual contract/delivery contract Virtual contracts are the buying and selling objects of contract transactions, which are uniformly formulated by contract
exchanges and specify standardized contracts for delivering a certain quantity of goods at a specific time. According to the type of margin, it can be divided into USDT margin contracts and currency based margin contracts; According to whether there is a delivery date, it can also be divided into perpetual contracts and delivery contracts. Delivery contracts can be further divided into different contract trading products such as current week, next week, current quarter, and next quarter based on the length of the delivery period.