All 3 Uses

illustrate
in
Heaven Is for Real
(Edited)

For one thing, a pastor's wife has to put up with being used as a sermon illustration a lot.
Chpt 17 *

illustration = example (to help clarify or demonstrate)
As we knelt on the floor to pray, I laid the book aside on the carpet, and it fell open to an illustration that pictured King Solomon sitting on his throne.
Chpt 18 *

illustration = picture
Or a kid with a brand-new box of crayons illustrating his science lesson: ROY G BIV.
Chpt 19

illustrating = drawing pictures to accompany

Definitions:

(1) (illustrate as in: as illustrated by this example)
to help make clear -- typically by example
(2) (illustrate as in: an illustrated children's book)
to draw pictures (or provide photographs) to accompany a book or other writing
(3) (meaning too rare to warrant focus)