Interaction design crafts the dialogue between a person and a system: what can be done, how the system responds, and how this loop of actions and reactions builds meaningful usage and differentiation.

The term was coined in the late 1980s by Bill Moggridge and Bill Verplank, just as the computer stopped being a machine to program and became an object to converse with. Interaction is this beautiful back-and-forth: I act, the system reacts, I understand, and I act again.

The absolute cornerstone of this discipline is feedback. An action without a clear reaction breaks the dialogue: a button pressed that shows no response leaves the user in doubt—should they try again, or did it fail? Don Norman turned this into a core principle: the system must constantly convey where we are and what is happening. A machine's silence is never neutral; it creates friction. Designing high-end interaction means perfecting the reaction just as much as enabling the action.

This feedback loop also carries time and rhythm: latency, the seamless animation explaining a transition, the micro-feedback of a subtle gesture. An outstanding interaction is felt as much as it is seen, because it beautifully respects the pace of human thought.

Our philosophy: a successful interaction is a dialogue where the user is always empowered, because the system responds clearly and in perfect tempo. The reaction is never a technical detail—it is half of the entire experience.

What else is at play: affordance and signifiers, UI, UX, cognition (the rhythm of thought), and attention.

References: B. Moggridge & B. Verplank, birth of "interaction design" (late 1980s); D. Norman, feedback principle.