There is a cost in buying and selling stock index futures. It's not that money won't change without moving. So the longer the time, the more the time cost of funds. Generally speaking, the price of forward contracts will be higher than that of recent contracts.

Futures and spot are completely different. Spot is actually a tradable commodity. Futures are mainly not commodities, but standardized tradable contracts with certain mass 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.

The delivery date of futures can be one week later, one month later, three months later or even one year later.