The essence of futures is to sign forward contracts with others to buy and sell goods (or stock index, foreign exchange, interest rate) in order to preserve value or make money. Futures can be short, sell first, buy and close after falling, and earn the difference. If you think the futures price will go up, go long (buy and open positions), go up (sell) and close positions, and earn: price difference = close positions-open positions. If you think the futures price will fall, short (sell the position), fall (buy) and close the position, and earn: price difference = opening price-closing price.