What is the Nash equilibrium in poker?

A Nash equilibrium is a set of strategies, one per player, where no player can improve their result by changing their own strategy alone. In poker, “GTO” and “Nash equilibrium” describe the same target: a strategy that can't be exploited, only matched.

The term “Nash push/fold chart” is often used more narrowly, for the classical heads-up shove/call equilibrium computed from pot odds alone, with no other players and no real tournament payout structure priced in. The multiway charts on this site are the same underlying idea, generalized: a genuine equilibrium solved for a full 6-max or 9-max table, using the real chip-EV or ICM payoff at that table rather than the simplified heads-up approximation.

The distinction matters more than it sounds. A heads-up Nash chart has a closed-form answer, which is why the classic tables have been copied around for two decades. A six-handed table does not: each player's best response depends on every other player's range, so the equilibrium has to be found by iteration rather than solved directly. That is what a solver is doing when it runs - repeatedly best-responding until nobody's strategy is improving any more.

Two things “unexploitable” does not mean. It does not mean maximally profitable: against an opponent who folds far too often, an equilibrium strategy leaves money on the table that a deliberate exploit would collect. And it does not mean the opponent cannot win - it means they cannot win by changing strategy, which is a much narrower claim. Equilibrium is a floor on your result, not a ceiling.

The practical consequence is that equilibrium ranges are the right default against unknown opponents and the wrong default against a read you actually trust. Knowing the equilibrium first is still the prerequisite, because an exploit is defined as a deviation from it - you cannot deviate deliberately from a baseline you do not know.