How are internal combustion engine and heat engine related?

An internal combustion engine is a specific type of heat engine that converts the chemical energy of fuel into mechanical energy through combustion. In this process, fuel is burned within the engine's cylinders, producing hot gases that expand and drive pistons. Both internal combustion engines and heat engines operate on the principle of converting thermal energy into useful work, but not all heat engines are internal combustion engines; other types include steam engines and external combustion engines.