What is Holography For Engineering Physics:
Holography is “lensless photography” in which an image is captured not as an image focused on film, but as an interference pattern at the film. Typically, coherent light from a laser is reflected from an object and combined at the film with light from a reference beam. This recorded interference pattern actually contains much more information that a focused image, and enables the viewer to view a true three-dimensional image which exhibits parallax.
That is, the image will change its appearance if you look at it from a different angle, just as if you were looking at a real 3D object. In the case of a transmission hologram, you look through the film and see the three dimensional image suspended in midair at a point which corresponds to the position of the real object which was photographed.
These three images of the same hologram were taken by positioning the camera at three positions, moving the camera from image no. 1 to 3.
Note that the pawn appears on the right side of the king in the left photo, but transitions to the left of the king as you move the viewing position across the hologram so that you are viewing it from further to the right. This is real parallax, which tells you that the image is truly 3-dimensional. Each perspective corresponds to looking through the hologram at a particular point.