What is a radio button?

Radio buttons are used for choices that exclude each other, typically yes / no questions where only one option can be selected at a time. Radio buttons must always have at least two alternatives, and it is required to choose one. Therefore there is always a default value that cannot be removed. 

For radio buttons to have a function you must have more than one product to choose from. The difference between radio buttons and checkboxes is that radio buttons only allow one choice, so the customer can only choose one of the possible products. Note that it is also not possible to select no products. An example would be the choice of a main dinner course – you cannot choose both a meat and vegetarian dish, and everyone must choose something (it is expected that everyone will eat).