A cartoon is a type of two-dimensional illustration, possibly animated. While the specific definition has changed over time, modern usage refers to (a) a typically non-realistic or semi-realistic artistic style of drawing or painting, (b) an image or series of images intended for satire, caricature, or humor, or (c) a motion picture that relies on a sequence of illustrations for its animation. An artist who creates cartoons is called a cartoonist. The concept originated in the Middle Ages and first described a preparatory drawing for a piece of art, such as a painting, fresco, tapestry, or stained glass window. In the 19th century, it came to refer to humorous illustrations in magazines and newspapers, and after the early 20th century, it referred to comic strips and animated films.