Holography is the science of producing holograms. It is an advanced form of photography that allows an image to be recorded in three dimensions. The technique of holography can also be used to optically store, retrieve, and process information.
It is common to confuse volumetric displays with holograms, particularly in science-fiction works such as Star Trek, Star Wars, etc. Also, the "holograms" appearing in identity documents, credit cards, and banknotes are not true holograms. Their apparent depth comes from stereoscopy. If you turn the "hologram" upside down, the depth of the image is inverted. Further, all depth disappears if you rotate the image 90° or if you look at it with only one eye. This is not the case with true holograms, which are not based on binocular vision but in the reconstruction of a virtual image. True holograms give the same 3-D images when viewed at any angle or with only one eye.