The essence of futures is to pay a certain margin and sign a long-term contract with others to buy and sell goods (or stock index, foreign exchange, interest rate) in order to achieve the purpose of maintaining value or making money.

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.

When you open a position (sign a sales contract), you should pay a deposit, and when you close the position (terminate the sales contract), the deposit will be returned to you.