We don't have the goods on hand, but we have to hang a sales slip first. When the price reaches the ideal price. Buy again. One selling and one buying is called liquidation. The previous selling behavior was "short selling".
Short selling means that you have no money on hand. However, I bought it in the market, sold it quickly before delivery, and used the money sold to deliver the money I bought earlier. The difference between one in and one out. Lose money or make money.