Electrodes were passing insulator (insulator) ceramics were found on the outside. This isolator serves to protect the central electrode of the electrical leakage and protect from engine heat. To prevent gas leaks are seals (seal) between the center electrode and the insulator between the body of the spark plug insulator.
Body is made of steel and plugs are usually given a nickel plate to prevent corrosion. The top of the outer body shaped hexagon (hexagon angle) which serves to harden (put) and loosening (opening) plugs. At the bottom is made of screw that can be screwed plugs (installed) to the cylinder head. At the lower end there is a spark plug electrode or the negative electrode side. These electrodes are welded to the body of the spark plug for a path to the future when there is a spark. There are two types of seat (seat) plugs is flat and cone-shaped. Stand spark plugs are part of the body at the top of the thread that will meet / paired with the cylinder head. If the spark plugs seat is flat, then there is a ring seals (sealing washers), otherwise if the holder does not require the conical ring seal.