a couple simple questions

haha, i have a couple stupid questions...

-what exactly are projectors and how are they different from just normal headlights?
-how do projectors work vs. normal headlights (i have a 95 accord)
-what's the difference between "halo" or "angel eye projectors" and other or jdm projectors?

oh yeah, also, why do angel eye projectors have that blue lense ball looking thing in the middle?

http://www.x3racing.com/headlights/94-97AccordBC1pProj_ya.jpg

ok, ONE MORE QUESTION. are any types of housings more "compatable" or effective with HIDs? and which is better in general.

THANKS! :)

Projectors for the most part, are just kinda brighter, concentrate more on a particular spot on the road. ( the individual circles all aim at thier own specific spot ) I got some 90-93 accord projectors for my 91 civic sedan, installin em' right now, but im not sure if there's a difference between halo and angel eyes, all i know is the light makes a circle instead of a ball shape.