Futures companies, also known as market makers, are the intermediary roles of bulls and bears. The main way for futures companies to make profits is to earn "intermediary fees" between buyers and sellers. To put it mildly, futures companies are pimps.

When you don't have "anything" but want to short, this pimp can lend you the "real thing" first. If the price of this physical object really drops, you will earn the falling price difference.

Specific short-selling steps: you take a bearish view on a futures, first borrow this futures from a futures company, and the futures in the market really fall, so you earn the price difference that falls in the middle, then buy futures at a low level and return them to the futures company, and the whole transaction is over. On the other hand, if you are short, this futures will not fall but rise, and it will be a big loss! But you still have to buy the futures and return them to the futures company.