An option on a futures contract gives the holder the right to enter into a specified futures contract. If the option is exercised, the initial holder of the option would enter into the long side of the contract and would buy the underlying asset at the futures price. A short option on a futures contract lets an investor enter into a futures contract as the short who would be required to sell the underlying asset on the future date at the specified price.

Essentially, the futures specified in the option contract allows someone to enter into the specified futures contract when the option expires.