Perpetual futures
A perpetual future is a contract that tracks an asset’s price without ever expiring. You never own the asset: you hold a position that gains or loses as the price moves.
Long and short
A long position gains when the price rises and loses when it falls; a short gains when it falls. Profit and loss is the size of the position times the change in price: a 2 BTC long gains $2,000 when BTC rises by $1,000.
Unrealized PnL is the gain or loss on a position still open. It becomes realized when you close it.
No expiry, and funding instead
A dated future converges on the spot price at expiry. A perpetual never expires, so it is held near the spot price another way: funding, a regular payment between longs and shorts. When the perpetual trades above the asset’s price, longs pay shorts; when below, shorts pay longs. The Funding rates article explains how Hyperliquid computes it.
Mark price and oracle price
Hyperliquid tracks two reference prices besides the last trade. The oracle price follows the asset’s spot price on major external exchanges. The mark price combines external prices with Hyperliquid’s own order book, and it is the price that unrealized PnL, margin and liquidation are measured against — so a brief spike in one trade does not liquidate anyone.
Leverage
Leverage lets a position be larger than the margin behind it: at 10×, $1,000 of margin holds a $10,000 position. Gains and losses are on the whole position, so a 10% move against a 10× position wipes out its margin. Margin, leverage and liquidation covers the rules.