Concepts by Donald Norman - www.jnd.org
Interaction Design exists as the design of behavior, bounded by three core interests: Human, Technical and Aesthetic. Interaction design is the branch of user experience (UX) design that illuminates the relationship between people and the machines they use. While interaction design has a firm foundation in the theory, practice, and methodology of traditional user interface design, its focus is on defining the complex dialogues that occur between people and interactive devices of many types-from computers to mobile communication devices appliances. Best practices in interaction design can be described with an Interaction Design Pattern (welie.com).
The term affordance refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used. Affordances provide strong clues to the operations of things. Plates are for pushing. Knobs are for turning. Slots are for inserting things into. Balls are for throwing or bouncing.
Interaction Design Example - Key to Shapes www.jjg.net/ia/visvocab/
Benefits of Interaction Design
Good interaction desgin makes use of known patterns that resonate with
users. When the proper pattern is used, the focus for the user is directed
towards the information instead of how to get to the information. When affordances
are taken advantage of, the user knows what to do just by looking: no picture,
label, or instruction needed.