Xenon technology provides a white and brilliant light, with a precise beam for better visibility and greater safety. 
Xenon lamps provide in general a longer lifetime than halogen lamps.

Xenon lamp light arcXenon lamp elements

What is xenon? It is one of the filling gases that gave the lamp its name.

To start the arc, you need a starter which ignites a flash between the electrodes (cathode and anode). 
The arc is a self-sustaining gas discharge between the electrodes.

A ballast converts the low voltage of the car battery to the operating voltage of the xenon HID lamp (HID = High Intensity Discharge).

Xenon types overview