Futures contract
A futures contract is an agreement to buy or sell an asset at a set price on a set future date. Both sides are bound, and each puts down only a deposit, called margin.
Futures are either deliverable, ending with the real asset changing hands (crude oil on CME), or cash-settled, ending with a payment of the price difference (stock index futures, crypto futures). Most traders close their position before expiry. A perpetual future has no expiry at all.
Learn more: classes of instruments and spot vs futures.