A button indicates a possible user action
A typical button is a rectangle or rounded rectangle, wider than it is tall, with a descriptive caption in its center. The most common method of pressing a button is clicking it with a pointer controlled by a mouse, but other input such as keystrokes can be used to execute the command of a button. A button is not however always restricted to a rectangular shape. The sole requirement of button interaction is that the user can execute a command by a click action. Thus pictures and background areas can be programmed as buttons. When pressed, in addition to performing a predetermined task, buttons often undergo a graphical change to mimic a mechanical button being depressed.
