Step-by-step explanation:
By definition the difference between a confederation and a federation is that the membership of the member states in a confederation is voluntary, while the membership in a federation is not.
Sometimes confederation is erroneously used in the place of federation. Some nations which started out as confederations retained the word in their titles after officially becoming federations, such as Switzerland. The United States of America was a confederation before it became a federation with the ratification of the current U.S. constitution in 1788