Informational Graphics explain relationships and systems using symbols and texts.
Instructional Graphics explain processes and functions using diagrams and texts.
In general terms, both approaches have some overlaps, and employ a combination of several didactic functions:
Relational: how components and parts relate to each other and render the whole system, structure or process
Descriptive: display the appearance of an object or component
Expressive: evoke an emotional response from the viewer
Functional: present steps in a process or the organization of a system
Logical: display abstract and mathematical processes and data
Analogic: represent a variety of relationships and possibilities
Representational graphics vary in detail from line drawings to photographs, but are alike in that they closely “resemble” the object(s) they depict. For example, a stick figure can represent a person.
Symbolic graphics show one thing and by analogy imply something else. For example, a graphic of a sword might be shown to illustrate the concept of medieval warfare.
Arbitrary graphics include tables, charts, and cognitive maps that have no real-life counterpart that they are attempting to portray.
Concise, well-edited text is used, with complex material subdivided into memorable packets.
Distractions, in both text and graphics are removed.
Relationships are clearly laid out and their nature reflected by the quality and form of connecting lines, arrows and other shapes.
Alignment of text and image reflects the purpose of the design.
Consistency of design establishes a sense of familiarity and place.
Density and space are carefully balanced to maximize eloquence.