Perpetual future
A perpetual future is a futures contract with no expiry date, kept close to the spot price by regular funding payments between longs and shorts. It is the most traded instrument on crypto exchanges.
When the perpetual trades above spot, longs pay shorts; when it trades below, shorts pay longs. Holding a perpetual therefore has a running cost or income, the funding rate, on top of the price move.
Learn more: what is a perpetual futures contract? and funding rate explained.