Futures contracts are contracts signed by investors and futures exchanges. When the delivery is due, it must be delivered with the futures exchange. If you buy, you must take cash to the warehouse designated by the futures exchange to pick up the goods. If it is for sale, it is necessary to take all the goods to the exchange for sale, and then collect cash. In addition, stock index futures are delivered in advance. If it is a loss, it will be paid to the exchange. If it is a profit, the exchange will also give you a corresponding profit.