Illustration
noun
1. Artwork that helps make something clear or attractive
2. Showing by example [syn: exemplification]
3. An item of information that is representative of a type
4. A visual representation (a picture or diagram) that is used to make some subject more pleasing or easier to understand
 
“illustration.” WordNet® 2.1. Princeton University. 21 Mar. 2007. <Dictionary.com http://dictionary.reference.com/browse/illustration>.