A future contract is an agreement that obliges the two parties involved to buy or sell a number of goods or assets, in a stipulated future date with a fixed rate pre-established.
The future contracts are a category inside the derivative contracts.
Two reasons to be interested in Futures/Forwards:
Hedge or Coverage Transactions:
The firm involved has or will have an underlying asset/good (Dollar, Brazilian Real, Soy, Wheat, etc) and will sell it in a future. With the transaction he can fix the rate for today for a transaction of tomorrow.
The client that contracts the forward, only wishes to speculate with the evolution of its value/price since the contract date till the expiration date.