Definition
A graphical user interface (GUI) lets people operate a computer through visual elements such as windows, icons, menus and a pointer, instead of typing commands into a text-only terminal. Rooted in research at Xerox PARC and popularized by the Apple Macintosh and Microsoft Windows, it became the dominant form of desktop interaction.
How it works
A GUI relies on the metaphor of “point and see”: on-screen icons and windows stand in for files and programs, and the user acts on them by pointing, clicking and dragging with a mouse or touch input. The system listens for these input events, updates the interface state and provides visual feedback.
Usage
Desktop and mobile operating systems, the web and most application software treat the GUI as the primary mode of interaction. Software aimed at a general audience usually offers a GUI first, because it lowers the learning cost.
Related and confusable terms
A GUI is one concrete form of UI, which covers any human–machine interaction surface, including command lines and voice interfaces. UX goes further, concerning the whole process and feeling of using a product rather than the interface alone.