Normal mapping completely deforms a mesh, where as displament mapping just moves the mesh "in" and "out" from it's original shape.

Imagine trying ti make a pyramid into a ball with displacement mapping.. it couldn;t be done, however it COULD be done with normal mapping.

Gamma correction for linear rendering (I think) is kinda of like light balancing renders to each other.. take your digital camera, face towards the sun, and take a pic. Now turn 90 degreees right, and take a pic so parts of the images overlap.

Bring those into photoshop, and look at the overlapping areas.. one will be MUCH darker then the other. That because the overall exposure changed. gamma adjusting that second pic will bring it in close to the first pic, so they could be easily blended together.

I'm thinking we see the same effect when animations are rendered in poser ,and this adjusts it.

Course I could be clueless about it.. hehee!

Way too many people take way too many things way too seriously.