(from lat. illustrare).
Concerning its definition, an illustration should elucidate a text to make it more understandable.
The function of an illustration is to tell a story using an image. A good illustration must guide the viewer through a visual path that tells him or her aim of the illustration. With just a glimpse, the observer should get an idea about the theme and the atmosphere the illustration wants to evoke. Furthermore, both the composition and the design of an illustration are very important, as well as the colours used, which will awake different sensations to the observer.