Funding Rate
The funding rate is a periodic payment between longs and shorts on a perpetual future that keeps it close to the spot price.
If the perpetual trades above spot, the funding rate is positive and long positions pay short positions; if it trades below, shorts pay longs. The payment is a small percentage of the position, settled every few hours depending on the exchange.
For a trader the rate is a running cost or income. For everyone else it is a gauge of positioning: a high positive rate means leveraged longs are crowded, which can make the market vulnerable to a sharp drop and a wave of liquidations.