Alpha-Beta Pruning is an optimization technique used in minimax algorithms to reduce the number of nodes evaluated in a game tree. It helps determine the best move for a player while minimizing the number of possible moves that need to be considered. By eliminating branches that won't affect the final decision, it speeds up the process of finding the optimal move. This method works by maintaining two values, alpha and beta, which represent the minimum score that the maximizing player is assured of and the maximum score that the minimizing player is assured of, respectively. If a node's value falls outside this range, it can be pruned, or ignored, thus enhancing efficiency.