Illustration
An illustration is a drawing, photograph or other type of image that is placed to support the text of a book, article, web page or advertisement. On the one hand, an illustration makes clear what the text is about even before reading. On the other hand, the illustration serves as an explanation after reading (part of) the text.
The illustration can contain information or additional explanation on its own, as in an infographic. Illustrations can also have a more decorative or contemplative function, as in a cartoon or stock photo.
Someone who provides illustrations for a book is called an illustrator.
