A moving picture is an illusion that makes a still photo seem to move. The basic principal behind motion pictures is the fast transition between one picture to the next, almost creating a seamless transition. A flip-book is a good example of this. Another example would be film used for old movies. The film contains negatives of an image which when light is shined through creates a "shadow" of the image. If you quickly transition the film from one image to the next you end up a motion picture.
