A chess engine is a computer program designed to play chess at a high level. It evaluates positions on the chessboard and calculates the best possible moves using complex algorithms. These engines can analyze millions of positions per second, making them valuable tools for players of all skill levels, from beginners to grandmasters. Many chess engines are used in online platforms and tournaments, providing players with insights and analysis of their games. Popular examples include Stockfish and AlphaZero, which have significantly advanced the understanding of chess strategy and tactics through their powerful computational abilities.