You'd have got more response to this if you'd posted as a new question
Standard lamp works by having electricity pass through a thin wire filament causing it to heat and glow white hot
HID (High Intensity Discharge) works by high voltage electricity arcing between two contacts in a very high purity inert gas envelope.
All you really need to know is that:-
1) HID = way more light for the same power consumption, about 5 times as much from a 50 watt HID compared with a 55 watt standard item.
2) To generate the high voltage and cause the HID to "strike" each lamp needs a little box of electronic wizardry.
3) Prices are silly cheap now, I paid over £200 for a two lamp conversion set and think it's the best money I have ever spent just for the safety aspect of seeing where you are going, you can get a kit now for less than £100 for 2 lamps, probably way less!
4) The lights are not on the EU list of approved light sources for motor cycles but as far as I understand that does not mean that they are illegal. I don't know of anyone in the UK who has had a problem. Properly adjusted they offer a huge improvement in safety for the rider and that has to be hard to argue against.
5) The HID lamps have a very long life expectancy as there is no filament to fail through vibration etc.
Do a search on the site for HID and you will find dozens of people who have fitted them (a really simple job) and are ecstatic with the results.
I had considered fitting a light bar with 2 additional lights each for dip and headbeam, a common mod, but after fitting HIDs I just didn't feel that I needed them any more.