A user interface, also called a “UI” or simply an “interface,” is the means in which a person controls a software application or hardware device.
A good user interface provides a “user-friendly” experience, allowing the user to interact with the software or hardware in a natural and intuitive way.
Nearly all software programs have a graphical user interface, or GUI.
This means the program includes graphical controls, which the user can select using a mouse or keyboard. A typical GUI of a software program includes a menu bar, toolbar, windows, buttons, and other controls.
The Macintosh and Windows operating systems have different user interfaces, but they share many of the same elements, such as a desktop, windows, icons, etc.
These common elements make it possible for people to use either operating system without having to completely relearn the interface. Similarly, programs like word processors and Web browsers all have rather similar interfaces, providing a consistent user experience across multiple programs.