A game tree is a graphical representation used in decision-making processes for games, illustrating all possible moves and outcomes. Each node in the tree represents a game state, while the edges represent the possible actions players can take. The root node starts with the initial game state, and branches extend to show subsequent states resulting from player decisions. Game trees are particularly useful in strategic games like chess or tic-tac-toe, where players alternate turns. By analyzing the tree, players can evaluate potential strategies and outcomes, helping them make informed decisions to maximize their chances of winning.