Nice Work! I love the contrast in the 2nd photo! As far as HDR goes it stands for High Dynamic Range.
"set of techniques that allows a greater dynamic range of luminances between light and dark areas of a scene than normal digital imaging techniques. The intention of HDR is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows." --From Wikipedia, http://en.wikipedia.org/wiki/High_dynamic_range_imaging
Here is my take on a single image HDR made with Adobe Camera Raw, No Photoshop.(Not a real HDR)
Before:
After:
Hope I didn't hijack your thread just trying give an explanation.