In the Lightwave manual they say that HDR (they call it HDRI high dynamic range illumination) means that Lightwave calculates intern with more than only the RGB colors. That means they can use numbers for each channel that has more than 256. They can create images that could be displayed better than your monitor actually can. It can mean that total black or total bright is not really 0,0,0 or 255,255,255. It can be something different.
So HDR is more accurate with lighting. Whatever effects they create theses effects are only a result of HDR calculating. These effects are not HDR.