An internal combustion engine is a heat engine that converts the chemical energy stored in a fuel into mechanical work through controlled combustion. This process occurs within a confined space, typically involving a piston moving within a cylinder. The energy released by combusting the fuel creates high pressure and expanding gases, which forcefully drive the piston. Many designs operate on cycles involving intake, compression, power generation, and exhaust. The resultant linear motion of the piston is usually converted into rotational motion through a crankshaft, providing power to transmit machinery. These engines are fundamental power sources used in transportation and various industrial applications.