Radio Buttons are very useful when you need your form users to select only one option from a list of options, they are very popular in almost all web forms.
If your radio buttons list does not include what your user needs to select, you might need a way of engaging the user to populate your radio button options - This is what User Contributed Radio Buttons is about.
Your form users can add their own options should they see that what they need to select is not included by clicking add option.
This will open a dialog box for them to add in the missing radio button option.
You can delete contributed options in the form builder by clicking on the red X next to the option.