Instead of betting on an outcome, you post buy and sell orders on both sides of a market and earn the small gap between them (the bid/ask spread) as other traders trade against you. You make money on the spread over many fills, like a shop earning markup on volume. The main risk is inventory: if you end up holding too much of one side, you can lose if the price runs against you, so a fair-value estimate and position limits keep you balanced.
Markets on Polymarket where market making / liquidity provision is the natural play:
