HID bulbs are filled with a Xenon gas mixture inside a center globe chamber.
When turned on, high voltage (42V-85V) is applied to the lower and upper electrodes, which creates an arc inside the globe.
The arc burns inside the Xenon gas-filled globe, and this produces a brighter, whiter light than a halogen bulb.
HID lights actually use less power but put out more light than halogen headlights. However, they need very high voltage to ignite the electric arc that provides the light source.
An electrical ballast, starter, and shielded cable (for safety) are combined to provide the initial high voltage required.
The additional electrical and hardware requirements make Xenon HID lights more expensive than halogens, and so for many years, they were primarily seen on luxury and high performance vehicles.
Only vehicles that have HID headlamps can use HID lighting. Vehicles can not switch from halogen to HID technology by simply changing the light source.
