What is a Protection Bet in Poker?

A protection bet is a bet made with a strong yet vulnerable hand that forces other players who are on draws to either call with unfavorable pot odds or fold.

For example, if you hold 9♥ 9♦ and the flop comes 8♠ 6♠ 2♣, you might put out a protection bet to prevent other players from hitting outs (like overcards, flushes and straights) on later streets.