Short selling is what we usually call short selling. Short selling refers to selling stocks that investors don't own (or borrowing from investors' accounts) and hoping to buy the stocks at a lower price in the future.

In short selling, brokers must borrow shares or arrange for the delivery of shares borrowed by other parties. When the stock price is expected to fall, you can buy these sold stocks at a lower price. If the subsequent buying price is lower than the selling price, the net difference between them is profit.