For information on radios, see Radio.
In computing, a radio button is a graphical user interface element
(widget) that indicates that it is one of a set, which together provide a multi-way choice which can be edited by the user. Radio buttons are arranged in groups of two or more and displayed on screen as, for example, a list of circular holes that can contain white space (for unselected) or a dot or (for selected). Adjacent to each radio button is normally shown a caption describing the choice that this radio button represents. When the user selects a radio button, any previously selected radio button in the same group becomes deselected. Selecting a radio button is done by clicking the mouse on the button, or the caption, or by using a keyboard shortcut.
Radio buttons got their name because, when one used to select preset stations on a radio receiver physically instead of electronically, depressing one preset button would pop out whichever other button happened to be pushed in.
It is possible that initially none of the radio buttons in a group are selected. This state can not be restored by interacting with the radio button widget (but it may be possible through other user interface elements).
See also check box.