A derivative is a financial contract whose value comes from an underlying asset, market, index, or rate. The underlying can be a share, forex pair, commodity, bond, interest rate, index, or cryptocurrency.
A derivative gives you exposure to a market without owning the underlying asset directly. Common derivative products include futures, options, forwards, swaps, and CFDs, and you can hold them to speculate on price, hedge an existing position, or apply leverage.
A derivative is a contract, not the asset itself. When you trade one you hold a position whose price tracks the underlying market without taking ownership, whereas buying the underlying asset means you own it outright. Because the price is derived, the contract carries terms the asset does not, such as margin requirements and an expiry date.
You expect crude oil prices to rise but do not want to buy and store physical oil.
You buy a crude oil futures contract priced at USD 80 a barrel.
If crude oil rises to USD 85, the contract gains USD 5 a barrel. If crude oil falls to USD 75, it loses USD 5 a barrel, because its value is derived from the underlying crude oil market.