Positional and Endgame Concepts
Zugzwang
Definition
Zugzwang is a state where the player to move MUST move, and every legal move worsens their position. Zugzwang often determines the result in technical endgames (K plus P vs K, minor piece endings). A concept that does not exist in other games because chess does not allow "pass".
Usage and Example
Classic example: white king on c6, white pawn on c5, black king on c8. Black to move MUST move, and both Kd8 and Kb8 lose because the white pawn promotes smoothly. This is zugzwang.
Grandmaster Tier Context
T3 Competitive Local through T5 Master. If you understand zugzwang, you can convert K plus P vs K endgames perfectly. If not, many games draw when they should have been won.