Tic-Tac-Toe is a classic two-player strategy game played on a 3x3 grid. The objective is to be the first player to form a horizontal, vertical, or diagonal line of three of their symbols (usually X or O). Players take turns placing their symbol on an empty cell of the grid, and the game ends when one player achieves a winning line or when the grid is filled without a winner, resulting in a draw. Tic-Tac-Toe is a simple yet engaging game often used as a teaching tool for basic strategy and game theory concepts.