"A futures contract is an agreement to buy or sell an asset at a future date at an agreed-upon price"
Commodities: A commodity is a raw material that has value and is more or less in constant demand (think- milk, eggs, pork, beef, chicken, lumber, iron, salt, crude oil, coal, etc.).
Securities (Financial): A security is a financial product such as an interest rate, the price of a stock, the value of some kind of debt like CDOs.
A recent history of returns on commodities futures by year and type
Futures trading is simply buyers betting on the future value of some product from the sellers. In commodities this could be a day trader speculating that the price of oil is about to skyrocket and buying contracts for purchases of oil at a lower price (he/she hopes).
Remember that futures trading is not limited to commodities
In securities futures, an example would be a buyer entering a contractual agreement to purchase some amount of stock for an agreed upon price at some future date. This would be to the buyer's advantage only if the price of the stock price on the future date is higher than the price agreed to in the futures contract.
At the heart of this kind of trading (and one could argue all trading) is the idea of betting for (+) or hedging against (-) the inevitable fluctuation of future value.
Reference: https://finance.zacks.com/futures-vs-commodities-5663.html