I have 10000 shares in my hand, and you think it will fall. Then you borrowed 1000 shares from me, gave me 1000 interest, and then sold the shares. After three months, the stock did fall. You bought 10000 shares from the market and returned them to me. It's called selling before buying.
For you, at the beginning of the sale, 1 10,000 shares were sold100,000. Three months later, you bought it from the market and only spent 80 thousand yuan. That's equivalent to having100000 first, then paying 80000, and you earn 20000. After paying the interest of 1000, you earned 1009.
This is that shorting can also make money.