Funding rate
The payment rate that periodically changes hands between longs and shorts on perpetual contracts; it shows which way the crowd is leaning.
Positive funding: longs pay (price is above spot, buyers dominate). Negative funding: shorts pay. Extremely positive funding for a long time creates conditions where leveraged longs can get flushed out (a long squeeze).
For those holding positions, funding is a real cost; on an annualized basis it can reach 30-50%.