The user interface is the area where the user and an application interact. Any tool or machine has a user interface that is designed according to the user's needs.
A user interface can be as simple as a set of buttons, like those on a telephone or video recorder. In the computer world, a user interface can include a keyboard, a pointing device, and the items that appear on a display screen. The user interface, then, is the ensemble of hardware and software that lets a user and a computer communicate.