Perspective projection is a kind of drawing that uses a two-dimensional surface (ie paper) to graphically approximate the image of a three-dimensional object. The intention is to approximate visual perception and this is also sometimes called perspective drawing. Parallel projection is using lines of projection that are parallel in reality and in the projection plane. There is an ancillary category known as pictorals - pictorals show an object as viewed from a direction that reveals all three exes of space in one picture meaning that some liberties must be taken with distortion.
