Short is the opposite of long. Most of them are profitable when you buy low and sell high, so shorting when you sell high and buy low is profitable.

This is a typical futures short-selling mechanism.

For example, you are bearish on the late gold price. You have no gold in your hand now. You lend 1000 grams of gold to the exchange in the form of 1000% deposit and sell it to others. If the transaction price is 200 yuan per gram. Later, the price really fell, down 180 yuan. At this time, you can redeem the gold from the buyer at the price of 180 and return it to the exchange. You lend it out at the price of 200 yuan and return it to others at the price of 180. Don't you have 20 yuan in your hand as your profit at this time?