Ive been hearing alot about this HDRI lighting and i just followed the wiki tutorial on it. What i want to know is…What is it???. it says its a technique to create realistic lighting. but how does it do it. Dooes it place lights on different places on the scene??
afaik, it doesn’t use lamps at all, what it does is use a high dynamic range image’s colors to light a scene. imagine if light came from the whole sky, but not as much from dark areas as from bright areas
(watch as someone comes along and rules out my description 
)
all you really need to know is that it can make for very realistic outdoor scenes. and it takes forever to render.