Direct manipulation
Also: Shneiderman
Interfaces where you act on visible objects continuously and see the results instantly — drag, don't command.
Direct manipulation — a term Ben Shneiderman introduced in the early 1980s — describes interfaces in which the objects of interest are continuously visible, you act on them with physical-feeling gestures (drag, drop, resize), and the effects are immediate and reversible. Dragging a file to the trash instead of typing rm; resizing a shape by its handles instead of editing coordinates.
The deep ancestor is Ivan Sutherland's Sketchpad (1963), where you drew with a light pen and the system maintained your constraints live. The payoff is a tight feedback loop and a feeling of working with the thing itself rather than describing it from a distance.
Programming, strikingly, has resisted direct manipulation — we still mostly type descriptions of behaviour into text files and run them later. Closing that gap is the obsession behind live programming and much of the future of programming.