High-Dynamic-Range. Usually in photography. A set of techniques that allow a greater dynamic range of luminances between the lightest and darkest areas of an image than standard digital imaging techniques or photographic methods.
Basically, you can make an image show much more detail or properly expose every aspect of the image. This effect is
not possible in 1 exposure because of the nature of cameras.
The bad: A lot of people try to imitate this look and even label their extremely
overdone edited photos as HDR. When in fact they are
nowhere near an HDR image. Most of the time, they contain less dynamic range than even the original single image.