A radio button or option button is a type of graphical user interface element that allows the user to choose only one of a predefined set of options. When a user clicks on a radio button, it becomes checked, and all other radio buttons with same group become unchecked.
The radio button and the check box are used for different functions. Use a radio button when you want the user to choose only one option. When you want the user to choose all appropriate options, use a check box. Like check boxes, radio buttons support a Checked property that indicates whether the radio button is selected.