Final answer:
An interface is a collection of properties that specify formatting for a widget. It serves as a contract for how objects of a class interact with other objects, and in web development, CSS defines the interface for specifying the appearance and formatting of HTML elements.
Step-by-step explanation:
An interface is a collection of properties that specify formatting for a widget. In computer programming, an interface is a programming construct that defines a set of methods and properties that a class must implement. It serves as a contract for how objects of that class interact with other objects.
For example, in web development, CSS (Cascading Style Sheets) defines the interface for specifying the appearance and formatting of HTML elements. Using CSS properties like color, font-size, and border, you can define the formatting rules for a widget.