Illustration

Illustration

Illustration is a form of design that shows pictures along side text. The illustration is usually mainly drawings or sketchings that tell a narrative in one image. In Roald Dahl's books, which are mainly children's stories, he has his friend and artist, Quentin Blake,  draw a page or half a page image relating to the story. 

Illustration uses a range of colours varying from basics, blacks, whites and greys or other basic tones. To bright eye catching tones and shades used in illustrative drawings.
Illustration has been around for centuries dating from cave paintings to 15th-18th century to early 19th century to modern illustrative techniques.
Illustration is a very good narrative technique that can be used in conjunction with writing and instructions. 

Illustrations can hold different conveyed images ranging from detailed landscapes to sketched portraits with basic detail.

Illustration has different approaches and types. The main examples are: 

     Engraving 

     Etching 
     Intaglio
     Linocut
     Pen-and-Ink Illustration
     Sumi-E
     Woodcut
They are all similar yet quite different in the process used to create the illustrative design.

http://en.wikipedia.org/wiki/Illustration#Early_history