Favorite and favourite are different spellings of the same word. Favorite is the preferred spelling in the U.S., while favourite is preferred in all the other main varieties of English. These preferences extend to all derivatives, including favorites/favourites, favoritism/favouritism, and favorited/favourited. Favourite has been the preferred spelling in British English for several centuries, but this does not mean that favorite is a late arrival to the language or even American in origin.

They have the same meaning. "Favorite" is the American spelling, while "favourite" is used for example in British English.