A frame, or group box, is a type of box within which a collection of graphical control elements can be grouped, usually because the designer of the form believes the grouping looks better than leaving the items outside of a frame, or uses a frame to allow multiple uses of a widget which otherwise can only be used once (such as a checked radio button).
In HTML (where frame has another meaning, referring to an individually scrollable portion of a page), this kind of grouping box is called a fieldset after the HTML element of the same name.
In the image to the right, the top frame has no title. The two frames below have titles, and a radio button outside of them, presumably to select one or the other. The lower of the two boxes is dimmed, or disabled, indicating its widgets cannot be selected. Note that each of the frames (as well as the area outside of the frames) has a checked radio button, while normally only one of the buttons can be selected.
Note that any widget, including nested frames, can be placed inside of a frame, not merely radio buttons.