Plain meaning
Start with the shortest useful explanation before going deeper.
A periodic payment exchanged between holders of long and short perpetual contract positions to keep the perp price anchored to the spot price. When the perp trades above spot (positive funding), longs pay shorts; when below spot (negative funding), shorts pay longs. Funding is typically settled every hour on Solana perps platforms like Drift and Jupiter Perps. High funding rates create arbitrage opportunities.