A chess engine is a computer program that calculates chess position and chess moves. The chess engine decides what moves to make, but typically does not interact directly with the user. Most chess engines do not have their own graphical user interface (GUI) but are rather console applications that communicate with a GUI such as XBoard, WinBoard or glChess via a standard protocol. This allows the user to play against multiple engines without learning a new user interface for each, and allows different engines to play against each other.