On the delivery date, the price of the goods on that day must be different from the current price, so the seller can only buy the goods at the price on the delivery date, and only when he has the goods in his hand can he cash the transactions that have happened.
When a futures contract expires, it is actually performance, physical delivery and physical transaction.
Generally, the buyers and sellers of futures contracts don't need goods, but earn the difference, which is generally reversed. This difference in the actual execution of the transaction is the settlement price difference.
From my own understanding, I don't know if I understand ~