Well, it's the perception of changing position anyway. In our sense it just affects the offset of the normal map for the purposes of lighting, thereby giving the illusion of height, though no additional detail exists.
I was trying to simplify it to point out the difference between the two, cause he seems to be confused.
he still seems confused,
no, our height map is not used in anything even remotely related to bump mapping, normal mapping is very very similar to bump mapping, in fact so similar one could say it's the exact same thing using different source data, but normal maps tend to give better/more versatile results.
but the height map is used to distort texture lookup so that the bumps actualy look 3d, the lighting effects of the normal map to an extreemly good job of doing this on there own, but things in the distance move slower than things in the foreground, this is called parallax, and this is what the height map is for.
for example, if you have a trench on your texture and you fly along it normally the bottom of the trench will move at the same speed as the surface, this is incorrect, but parallax mapping (what the height map is for) will cause the bottom of the trench to move slower than the surface so it seems more 3d, gives a since of distance.
