Value bet
A bet made to get called by worse hands.
You raise A-K from the cutoff, the big blind calls, and the flop comes K-8-3 rainbow. She checks. You bet two-thirds pot with top pair top kicker — not because you're afraid she'll fold, but because K-J, K-9, and pocket pairs like jacks will call you here and probably on the next two streets. That is a value bet: you want the worse hand to stick around and pay.
This is where most of a winning player's money comes from. Bluffs scoop small pots nobody wanted; getting a strong hand paid off street after street by a worse one is the profit. But your size has to match what the loser can call. Fire a pot-sized bet into a range of second pair and ace-high and you fold out everything worse, which defeats the point of betting for value at all.
The common beginner mistake runs the other way: playing the best hand too soft. Checking back top pair on the turn to control the pot, or slowing down because a scary card might have hit. Most of the time that card changed nothing — the opponent's range is still full of hands that call — and a bet you skip is money you never see again. If you're ahead of what calls, bet. Folds don't help you here; they're value walking out the door. The point is getting paid.