A poker solver is a computer program using game theory algorithms to calculate Nash equilibrium strategies for specific poker situations. The most popular solvers include PioSOLVER, GTO+, Simple Postflop, and MonkerSolver. These programs allow players to analyze specific spots by inputting ranges, sizings, and board configurations to discover ideal bet, check, raise, and fold frequencies. Solver study has revolutionized modern poker, making these tools mandatory for serious mid-to-high stakes players.