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And now I am going to ask a very "dumb" question... just what ARE/is HDRI .... lights? and if so... still... what does it mean exactly? I know there is such a thing in Poser but I never really understood that lighting concept/type.

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Lyne

HDRI is High-dynamic-range imaging.  They can be used both for background and global illumination. 

Download one of the free ones and click on the Scene in the instances tab.  Select background and tell it HDRI and load the image.  You will not see anything until you render.

In the render room, check sky light and indirect light and the HDRI will illumiate the scene with no other lights.

ncamp