High intensity Discharge (HID) Work Lights derive their light from a plasma discharge rather than a filament. The bulb is a lot more resilient than a halogen bulb especially over rough terrain and conditions and has a much longer life > 2000+ hours.
The system involves a ballast to start the light and certain gasses to create the light. While it takes a few seconds until it reaches maximum light output the short wait is well worth it.
Overall the system uses less energy than halogen (35watts vs 100watts) , while producing 3 times as much light. The result is a far superior white light, less draw on your battery/system, and a bulb that needs replacing a lot less often.