1. What is HDR? HDR stands for high dynamic range. It uses the capability of modern displays to show the picture in high contrast. High contrast also gives pictures the impression of sharpness. HDR pictures support highlights and specular reflections, plus extended details in shadows and dark parts of the picture.
2. What is video dynamic range? Some people say that it is the ratio between the blackest black and the brightest white on a display. This is wrong because some OLED displays can have zero light output, which would give infinite dynamic range. This makes no sense.