Maya_D831, to phrase it a little simpler than in my previous post: Radio buttons are used to represent alternatives (mutually exclusive); check boxes are used to represent options (not exclusive).
The term "radio" is used because radio buttons "radio" (transmit) information to the underlying program and to distinguish them from regular buttons (also referred to as action buttons), the little rectangles which perform an action, like displaying the next page or performing a calculation, when pressed.
