Haha I have just come into contact with futures, so it may be easier for you to understand if I am a first grader. In fact, futures trading means buying and selling. Buying first and then selling means going long (you think the price will rise later), selling first and then buying means shorting (you think the price will fall later). No matter what, you have to go through one purchase and one sale. process.

"I still don't understand, isn't it buying low and selling high? Being short means being bearish, so what does it mean to sell if it falls?" This question is still in my own words. This "selling" does not refer to your previous purchase. To sell the goods, for example, suppose three people, you, me, and him, trade a ton of corn. Now the price is 1,800 yuan/ton. Sell it to me first (you are short because you think the price will fall. Why would I buy it? Because I think it will rise and go long). After 5 days, the price is 1,500 yuan/ton. At this time, do you think The price will not fall. You have already made 300 yuan, should you "sell" it? The person who 'buys' at this time may be me (I lost 300) or he (he thinks it will continue to fall and is short). In fact, there is no physical object (corn) coming and going in the buying and selling, it is just the transfer of the contract.