The differences are
- higher bit depth, which displays more colors, more shader, eliminates banding on gradients.

- higher luminance, meaning it can better simulate a broader rande of light intensities like having a sun and a point light in a scene, which would clip to the same luminance value in a SDR screen. Which is obviously incorrect.

- higher dynamic range, meaning it can better simulate what your eye can see in real life. Both darker and brighter details in a scene. Our eyes are pretty amazing and no camera or display can properly capture that yet. The game worlds are usually build with real life physical values for lighting, materials etc, and to get that photoreal quality, we need higher dynamic range monitors to be able to show that. Otherwise, you will see blownup windows in dark rooms, autoexposure adjusting etc.