A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. The ignition cables, also known as “spark plug wires” are part of the ignition system. They transfer the spark from the distributor or ignition coil to spark plugs that ignite the air-fuel mixture, starting the engine.