Leela Chess Zero is an open-source chess engine that uses artificial intelligence to play the game. It is based on deep learning techniques, similar to those used in AlphaZero, which allows it to learn and improve its gameplay by playing against itself. The engine is designed to evaluate positions and make decisions based on patterns it has learned from millions of games. Leela Chess Zero has gained popularity in the chess community for its unique playing style and has been used in various online chess platforms and tournaments.