There is a dIFference between the main company and the index contract: the futures index is calculated by weighting the volume of each contract, which is generally recorded as an index in commodities, but directly recorded as a weighted contract in CICC, such as if weighting. The main contract is the continuation of the main contract, that is to say, the main contract is the mechanical connection of all the main contracts, forming a continuous contract, with the largest daily trading volume and positions, which will form a relatively continuous K-line chart. Which is the main contract. The main contract is the connection of the main contracts in different periods, and the index is formed by weighting all contracts according to the volume. Obviously, there is a gap in the main contract because of the monthly change, and the index is the weight of all contracts, so there will be excellent continuity. Futures are mainly not commodities, but standardized tradable contracts with cotton, soybeans, oil and other bulk products and financial assets such as stocks and bonds as the targets. Therefore, the subject matter can be commodities (such as gold, crude oil and agricultural products) or financial instruments. The delivery date of futures can be one week later, one month later, three months later or even one year later. A contract or agreement to buy or sell futures is called a futures contract. The place where futures are bought and sold is called the futures market. Investors can invest or speculate in futures. Most people think that improper speculation in futures, such as short selling without goods, will lead to financial market turmoil, which is not correct. Going long and shorting at the same time is a healthy and normal trading market.