Illustration (noun)

1. A picture or diagram used to explain or decorate a text or a design.
2. Something serving to clarify or demonstrate, especially by example or analogy.

Origin:

Late 16th century (denoting a clarifying story or picture): from french, from latin illustratio(n-), from the verb illustrate "light up, explain".

Examples:

1. The textbook was filled with colorful illustrations.
2. His paintings served as illustrations for several children's books.
3. The data provided a clear illustration of the problem.
4. The illustration showed how to put together the toy.
5. The graphs and charts provided powerful illustrations of the trends.