1999-2000 Hyundai Elantra Headlights Set Driver Left Passenger Right Pair Halogen-Type Assembly

HID stands for "High Intensity Discharge". These bulbs use an electric arc rather than the glowing filament in a Halogen bulb. HID headlamp bulbs do not run on low-voltage DC current like a Halogen Bulb, so they require a ballast, which controls and regulates the flow of current. This ballast will require an ignitor to light the bulb. This is either integrated directly into the bulb or as a separate unit which is occasionally part of the ballast, similar to fluorescent bulbs in your home. In a vehicle, HID bulbs tend to be much more expensive to replace than a Halogen bulb.

Your old lights probably had moisture or condensation in them too, but the older, dulled and oxidized lens makes moisture less noticeable. Now that you have those new clear lights on your nice car, all of sudden you’re really looking at them, which is completely normal. Without going into too much detail, It's a fact that condensation happens just about anywhere. If there's a temperature difference between the inside and outside of the lens, moisture will occasionally develop, and, since your Halogen headlight bulbs put out some heat, the inside of the headlight is full of warm air while the outside is cooler. This is sort of like how the front window on your car can fog up and you have to turn on the defroster vent to clear it all away: The condensation in your headlights will usually dissipate after the headlights are turned on, as the heat of the lights evaporates the moisture. Your high beams will usually produce more heat to clear any condensation more quickly.

HID lights can also be referred to as Xenon bulbs (though not all Xenon bulbs are HID). Some vehicle manufacturers also use Bi-Xenon headlights, headlights which use an HID low beam bulb in combination with a halogen high beam bulb.