High Intensity Discharge(HID) is an arc lamp in which the bulb is a quartz glass tube filled with xenon gas and metallic salts with two electrodes inside, separated by a gap. When the arc jumps, it produces light.
This lighting system requires high voltage to cause the arc to jump (like a spark plug arc jumps). The ballast to the right of the lamp transforms 12V on your bike to 20,000V to the lamp. The black box to the left of the lamp is the control relay, required to make the HID bulb stay on continuously as the low beam. The 35W H11 bulb turns on for high beam and is primarily used to signal, or flash, on coming traffic. The HID bulb draws less current, only 35W, yet produces over ten times the luminosity. That's about 2,500,000 Candle power compared to approximately 24,000 candle power on your stock lamp.