The RadioButton control is one element of a radio button group.
The Group Name binds different radio buttons controls. All radio buttons with the same group name will interact. E.G. switching one on will switch others of the same group off.
Each radio button within a group must have a unique value.
One button within a group can be marked as the default value. This will set the button initially to on.
We could define radio buttons for colors. The group name could be "color" and we can set up different buttons with unique values like "red", "blue", "green", ...