Interaction Design
The creation and structuring of interactive behavior between users and a digital or physical system.
In practice
Interaction design shapes how a person and a system act on each other over time: what a person can do, how the system responds, and how each step leads to the next. It covers digital screens and physical products alike. Designing a thermostat's interaction means deciding what turning the dial does, how the display responds, and how it confirms that the new temperature has been set.
Often confused with User Interface (UI)
UI designs the visible controls and screens; interaction design defines behavior, how the system responds to actions and how steps flow over time.
Try this
Write down every step and response when you set an alarm on your phone, then mark the most confusing one.