This is a spark plug and it is used on various lawn equipment around your home. This part powers the engine by lighting the fuel and air mixture found in the cylinder of the engine. If the tip of the spark plug is damaged or burnt (also known as fouled), the engine will not start. This spark plug is Rcj7-8Y, that means this has a resistor type R, a shell design type CJ (14mm thread, 0.375 inch reach, 0.75 or 0.8125 inch hex), a heat range/application type 7-8 (heat range with automotive, small engine, and ordnance applications), and a firing end design of type Y (standard projected core nose). If your machine is not turning on, or is running extremely rough, you will need to replace the spark plug.