It's a song that was created in a traditional style in a country where it's originated from.
Explanation:
Folk songs do not specifically exist only in United States. Every countries in the world have their own folk song. Since each countries have a lot of difference of musical history and traditional instrument, folk songs contained a wide variety of styles.
During its earliest creation, folk song was created to tell a tale. Usually about the deeds of famous people in that era. But these days, folk songs could contain various themes just like any other genre.
