The principle of buying and selling is this: you pay a deposit and borrow his shares from the original owner of the stock (in fact, you, the securities company, the original owner of the stock) (you must sell them at some point in the future). For example, I have cash 1000W:

I borrowed the stock of 1000W from X with a deposit of 1000W, and then sold it at 10 yuan, so I got 10000 yuan. But I have to return some shares of X 1000W at some time in the future. What should I do? The key is to buy back 1000W shares and return them to X.

If the stock goes up, for example, 1 1 yuan, I will spend 1 1000W to buy back a stock and give it back to X. I lost 1000W, and I lost all my money. But if the stock falls, for example, 1 yuan, I can buy back a stock of 1 1,000 w with 9000W. At the beginning, I sold it at 10 yuan and10000 W. At this time, I got the cash of 1000 W and a stock of1000 W.