Generalized Input
The Wolfram Language's unique structure allows a generalized notion of input, in which not only ordinary text, but also typeset structures, diagrams, graphics, control objects, and even complete user interfaces can be entered and immediately return values that have been associated with them.
Controls as Input
DynamicSetting — display as a control that dynamically gives its setting when evaluated
— evaluate in place to show the displayed form
Checkbox ▪ PopupMenu ▪ ColorSetter ▪ FileNameSetter ▪ SetterBar ▪ ...
Manipulate — set up a collection of controls
Giving Interpretations
Interpretation — specify any interpretation for a graphic or other expression
Iconize — convert any expression to display in an iconized form
Graphics as Input
Graphics, Graphics3D — use any graphic as input
Input Annotation
Placeholder — label a place to type