HID, High Intensity Discharge, refers to lighting technology that relies on an electrical charge to ignite xenon gas in a sealed bulb, similar to the lightning phenomenon in the sky. HID lighting does not have a filament but instead creates light by igniting an electrical discharge between two electrodes in an air tight tiny quartz capsule filled with xenon gas. HID lighting are also called Xenon lighting, referring to the gas inside the bulb.

Comparison of HID & Halogen

The Xenon HID Bulb is a High Intensity Discharge Bulb filled with a mixture of "noble" gases including Xenon. Unlike a halogen bulb, the Xenon bulbs has no filament.
The light arc is created between two electrodes. As is the case with other gas discharge bulbs, the Xenon HID bulb has an electronic starter for quick ignition and requires an electronic ballast to function properly