An illustrator is a narrative artist who specializes in enhancing writing by providing a visual representation that corresponds to the content of the associated text. The illustration may be intended to clarify complicated concepts or objects that are difficult to describe textually, which is the reason illustrations are often found in children's books.
Traditional illustration techniques include watercolor, pen and ink, airbrush art, oil painting, pastels, wood engraving, and linoleum cuts. John Held, Jr. was an illustrator who worked in a variety of styles and media, including linoleum cuts, pen and ink drawings, magazine cover paintings, cartoons, comic strips, and set design, while also creating fine art with his animal sculptures and watercolor, many established illustrators attended an art school or college of some sort and were trained in different painting and drawing techniques. Universities and art schools offer specific courses in illustration (for example in the UK, a BA (Hons) Degree) so this has become a new avenue into the profession. Many illustrators are freelance, commissioned by publishers (of newspapers, books, or magazines) or advertising agencies. Most of the scientific illustrations and technical illustrations are also known as information graphics. Among the information graphics specialists are medical illustrators who illustrate human anatomy, often requiring many years of artistic and medical training.
A particularly popular medium with illustrators of the 1950s and 1960s was casein, as was egg tempera. The immediacy and durability of these media suited illustration's demands well. The artwork in both types of paint withstood the rigors of travel to clients and printers without damage.
Digital art 
Computers dramatically changed the industry and today many cartoonists and illustrators create digital illustrations using computers, graphics tablets, and scanners. Software such as Adobe Illustrator or Adobe Photoshop are now widely used by those professionals.
- Airbrush artist
- Archaeological illustration
- Architectural illustrator
- Fashion illustration
- Graphic designer
- List of illustrators
- Marker rendering
- Pictorial maps
- Storyboard artist
Societies and organizations 
- Society of Illustrators
- American Illustration
- Communication Arts
- Society of Children’s Book Writers and Illustrators
- San Francisco Society of Illustrators
- Society of Illustrators of Los Angeles
- The Association of Illustrators
- The Illustrators Partnership of America
- AIIQ - l’Association des Illustrateurs et Illustratrices du Québec
- Colorado Alliance of Illustrators
- The Association Archaeological Illustrators and Surveyors
- Guild of Natural Science Illustrators
- The Association of Medical Illustrators
- Guild of Natural Science Illustrators-Northwest
- Illustrators Australia
- French illustrators
- Stuttgart Database of Scientific Illustrators 1450-1950 (DSI) (currently 5000 entries)