@rgb HDR is not a matter of color range, it is a matter of dynamic range. That is, the ratio of maximum brightness to minimum brightness. With a digital camera, it is the ratio of "pure white" to that level of black where no detail can be seen behind the noise. With a monitor, it is the ratio of white to that "gray" that is called black, but we can still see the backlighting. (Well, with LED, of course, "black is black," but white is not the sun there, either.)

In numbers, the monitor usually has 10 f-stops (a term from photography, means two-to-some degree), the SLR has 14, the eye has more than 20. So to fully show what the eye sees, we have to take 2-3-5 shots to capture both dark and light areas equally well. That's HDR.

But to fit that into the monitor's range... Algorithms are applied that try to approximate the perceptual features, making the dark areas lighter and the light areas darker. This is called tonal mapping and is something that is often confused with the concept of HDR.