Perpetual contract
A futures contract with no expiry date, held to spot by periodic funding payments.
A perpetual — "perp" — behaves like a futures contract you can hold forever. There is no settlement date, no roll, and the position stays open until you close it or the margin runs out.
Because there is no expiry to force convergence, the contract is anchored by two mechanisms: a mark price computed from an index of several spot exchanges (so a single venue's wick cannot liquidate you), and the funding payment that makes it expensive to sit on the crowded side.
Perps are where most arbitrage volume lives: they are the deepest crypto markets, they exist on every major venue for the same coins, and each venue prices its own. Two perps on the same asset disagreeing is the most common route in the scanner.