Pot odds
The price the pot is offering: the fraction of the final pot you must contribute to call, expressed as the equity you need to break even.
Every bet is a price. Pot odds convert that price into a single percentage: call divided by the total pot after calling. Clear that number with your actual equity and calling shows a profit; fall short and folding is better. It is one half of nearly every postflop decision, with equity as its other half: the price tells you what you need, equity tells you what you have.