Is the futures with the stock index as the subject matter. After a certain period of time, the two parties trade the price level of the stock index and make delivery by cash settlement of the price difference. Stock index futures is a kind of financial futures. Stock index futures trading and stock trading are different. Compared with stocks, stock index futures have several distinct characteristics, which are particularly important for stock investors: futures contracts have an expiration date, and stocks cannot be held indefinitely after purchase, and the number of stocks will not decrease under normal circumstances. However, stock index futures have a fixed expiration date and will be delisted when it expires. Therefore, trading stock index futures cannot be equated with buying and selling stocks. After trading, we must pay attention to the expiration date of the contract to decide whether to close the position in advance or wait for the expiration of the contract (fortunately, the stock index futures are settled in cash and do not need to actually deliver the stock), or to transfer the position to next month. Futures contracts are margin transactions, and stock index futures contracts must be settled every day. Generally, you can buy and sell a contract by paying about 10- 15% of the contract face value, which improves the profit space, but on the other hand, it also brings risks, and you must settle the profit and loss every day. After buying a stock, the book profit and loss are not settled before selling. However, stock index futures are different. After the transaction, the contract held in hand should be settled at the settlement price every day, and the book profit can be withdrawn, but the book loss (that is, additional margin) must be made up before the opening of the next day. And because it is a margin transaction, the loss may even exceed your investment principal, which is different from stock trading. Futures contracts can be sold short. Stock index futures contracts can be easily sold short and bought back after the price falls. It is ok to short stocks, but it is relatively difficult. Of course, once the price rises instead of falling after short selling, investors will face losses. The market is highly liquid. Studies have shown that the liquidity of stock index futures market is obviously higher than that of stock spot market. For example, 199 1, the trading volume of FTSE-100 index futures has reached 85 billion pounds. Stock index futures are delivered in cash. Although the futures market is a derivative market based on the stock market, it is delivered in cash, that is, only the profit and loss are calculated at the time of delivery, and the physical object is not transferred. During the delivery period of futures contracts, investors do not have to buy or sell the corresponding stocks to fulfill their contractual obligations, thus avoiding the phenomenon of "crowding" in the stock market during the delivery period.