HID stands for High Intensity Discharge. These lamps produce light by means of heating a gas with an electric arc (as opposed to the incandescent lamp which produces light by electrically heating a solid wire - usually tungsten filament).

All HID light sources require auxiliary equipment (such as a ballast, capacitor, and/or ignitor) to provide the appropriate electrical values for starting and operating. There are many different types of HID lamps, each with its own characteristics and applications.