A piston is a cylindrical engine or pump component that fits tightly inside a closed cylinder, sliding back and forth to transfer force. In internal combustion engines, its primary job is to convert the energy generated from burning fuel into mechanical motion. As the fuel air mixture ignites inside the cylinder, the expanding high-pressure gases push the piston downward. This linear force is transmitted through a connecting rod directly to the crankshaft, transforming the up-and-down movement into the rotational energy that ultimately turns a vehicle’s wheels.