Spark plug

device that generates sparks in internal combustion engines

Also known as a "sparking plug", it's a device used in delivering the electric current to the air-fuel mixture in the combustion chamber in an internal combustion engine. It’s connected to the ignition coil and as the electricity flows through the coil, a voltage difference develops between the electrodes on the spark plug. This causes electricity to jump the gap, making a spark which ignites fuel.