Implied odds
The money you expect to win later if you hit, on top of what’s already in the pot.
You're in the big blind with pocket fives, facing a cutoff raise. The pot lays you about 3-to-1 on a call, but a pocket pair flops a set only about 12% of the time — 7.5-to-1 against. The price doesn't cover the odds. What covers it is the money still to come: if the flop comes 9-6-5 and the cutoff holds an overpair, he isn't folding to your set, and you can win a full stack on top of what's already in the pot. That extra money is the implied odds.
This is why stack depth matters more than the size of the current pot. Two players 100 big blinds deep have far more implied odds than two sitting on 20, because the payoff for hitting a hidden hand scales with what's left behind. It's also why disguised hands like sets and straights beat obvious hands like top pair for value: opponents pay off what they can't see coming.
The common mistake is counting money that isn't there. Calling a raise with a small pair against someone who folds to any bet, or against a stack too short to pay off a set, looks like set-mining but pays nothing — you're burning chips on a long shot with no reward behind it. Implied odds only count if the money is collectible. When it isn't, the call was losing from the start.