Lithography takes advantage of the stickiness of printer's ink and the way in which it repels water. An image is created in water-resistant material, such as waxy crayon on a flat limestone surface or metal plate. It is then bathed in water making everything except for the drawing wet. Printer's ink is applied that sticks to the drawing but not to the water. A piece of paper is then laid on top and sent through a press leaving an image imprinted on the paper.
An artist might commission a lithograph if he wishes to sell prints of a painting. The print will typically be numbered and signed in order to increase its value. The idea being that as the lithograph was commissioned by the artist it is very close to the original.
Some images are commissioned specifically for lithograph reproduction. This is especially true of comic images that will later be mass produced.