In software design, the look and feel of a graphical user interface comprises aspects of its design, including elements such as colors, shapes, layout, and typefaces, as well as the behavior of dynamic elements such as buttons, boxes, and menus. The term can also refer to aspects of a non-graphical user interface, as well as to aspects of an API – mostly to parts of an API that are not related to its functional properties. The term is used in reference to both software and websites.

A graphical user interface, or GUI, is a form of user interface that allows users to interact with electronic devices through graphical icons and visual indicators such as secondary notation. In many applications, GUIs are used instead of text-based UIs, which are based on typed command labels or text navigation. GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces (CLIs), which require commands to be typed on a computer keyboard.