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.

Futures and spot are completely different. Spot is actually a tradable commodity. Futures are mainly not commodities, but standardized tradable contracts with some bulk products such as cotton, soybeans and oil and financial assets such as stocks and bonds as the targets. Therefore, the subject matter can be commodities (such as gold, crude oil and agricultural products) or financial instruments.