Folk

Includes both traditional music and the genre that evolved from it during the 20th century folk revival. The term originated in the 19th century but is often applied to music that is older than that. Some types of folk music are also called world music. Traditional folk music has been defined in several ways: as music transmitted by mouth, as music of the lower classes, and as music with unknown composers. Starting in the mid-20th century a new form of popular folk music evolved from traditional folk music. This process and period is called the (second) folk revival and reached a zenith in the 1960s. This type of folk music also includes fusion genres such as folk rock, folk metal, electric folk, and others. While contemporary folk music is a genre generally distinct from traditional folk music, in English it shares the same name, and it often shares the same performers and venues as traditional folk music. Even individual songs may be a blend of the two.

Associated Sub-Genres: Traditional Folk, Contemporary Folk, Indie Folk, Neofolk, Progressive Folk, Anti-Folk, Freak Folk, Filk Music, American Folk Revival, British Folk Revival, Industrial Folk, Techno-Folk, Psychedelic Folk, Sung Poetry

Source: http://en.wikipedia.org/wiki/Folk_music#Specialty_sub-genres