Real Dictionary

illustrate
verb: If you illustrate a book, you put pictures, photographs, or diagrams into it.
verb: If you say that something illustrates a situation that you are drawing attention to, you mean that it shows that the situation exists.
verb: If you use an example, story, or diagram to illustrate a point, you use it to show that what you are saying is true or to make your meaning clearer.

illustrate in American English
to make clear; explain
intransitive verb: to clarify one's words, writings, etc., with examples
transitive verb: to furnish (a book, magazine, etc.) with drawings, pictures, or other artwork intended for explanation, elucidation, or adornment

illustrate in British English
verb: to clarify or explain by use of examples, analogy, etc