HDR photography is High Dynamic Range photography where technically photographers shot one object several times wish different stops and then merged together into one photo. The main idea with my own language is to eliminate light contrast or shading and look as realistic as possible.
Wikipedia describes: In image processing, computer graphics, and photography, high dynamic range imaging (HDRI or just HDR) is a set of techniques that allow a greater dynamic range of between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. This wide dynamic range allows HDR images to more accurately represent the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight, and is often captured by way of a plurality of differently exposed pictures of the same subject matter
Here are some examples that are ‘realistic’ and not overdone: