You're going to hear “GTO” everywhere. It sounds like something for mathematicians, but the idea is simple: a strategy so balanced that nobody can beat you systematically.
What it means
GTO = Game Theory Optimal. It's the equilibrium strategy: if you play it, no matter what your opponent does, in the long run they can't exploit you. It isn't always the most profitable against bad opponents, but it's the “mathematically correct” foundation.
Where does it come from?
From an algorithm called CFR (Counterfactual Regret Minimization). It's the engine behind solvers (PioSolver) and the bots that beat professionals (Libratus, Pluribus). The solver plays the game millions of times until it finds the equilibrium.
Why it mixes
A hallmark of GTO: it plays the same hand in different ways on purpose. Sometimes it raises AK, sometimes it calls. Why? So you can't read it. If it always did the same thing, you'd exploit it.