An illustration is a visual approach to a verbal story.
Is there any difference between art and illustration? In an illustration, there is little, if anything, for the viewer to do. All the information is there available for the viewer to see. There can be several themes at once but it precisely includes all the visual information the audience is expected to use upon viewing it. Illustration is easily given words to express it that are appropriate to it. Art is something else and represents a more interactive form of visual communication. It does require something from the viewer in order to be recognized. Art is not intended as a verbal communication represented in a visual format.