There are various definitions of what an illustration may be and to what kinds if illustrations there are.
There are just abundant information regarding this subject that you can easily get lost if you try to find it yourself.
But why would you do so if you can have a brief overview of it in the next lines?
First and foremost, an illustrator is different from a designer. Oftentimes, they are being interchanged by people. To give you a clearer idea of what these two people do, keep on reading.
Designer
A designer usually depends on set of elements to create stunning visual artworks. Then with these elements, they organize them to create engaging and attractive compositions. The primary task of a designer is to concentrate the viewer’s attention on visual concept, detail, idea, part of design and make the idea mark to people’s minds.
Illustrator
More often than not, they are producing imagery on themselves and not working on the entire design of the product. Illustrations are usually supportive to other mediums like for example, an illustration is typically accompanied by books, newspaper articles, magazines in which they serve their true purpose.
Illustrators are normally trying to strike a balance between text and visual art and avoid stealing the spotlight on illustration.