Photography, even digital is about compromises. A piece of film or a photosensor can only measure a small range of brightness. So a normal photograph can only accuratly reproduce the bright areas or the shady areas based on the exposure you use. ( all of this is over simplified ).
With HDR photography you are taking a series of photographs each one using a different exposure so some are recording the bright parts of the scene, some the mid tones, and some the shadows.
Now the cool part, that is combining the best parts of all of the photographs to come up with the images you are seeing.
I have seen the results and understand the theoratical aspects of doing this, but I have actually never tried it. Several of cmrncraz15’s images are as good as the ones I have seen displayed at a local gallery.