The requirements that are involved in an illustration job can be divided into two categories:

Content and Design.

Content is what is depicted in the layout and how it is treated stylistically. It may include photographs, artwork, text elements, graphics, and blocks of copy.

Design is the carefully considered placement of this content into a container of predetermined size and shape.

Does the design draw the casual viewer in?

How does the viewer experience the flow of visuals and information?

Does the design have the desired effect of releasing the viewer to explore additional content (turn the page)?

These two aspects of picture-making are dependent on the context that the illustration is being used within.

Furhermore, content and design should be considered synergistically. That is, one side cannot be fully explored without that process being informed by aspects and limitations of the other.