Folk music is an English term encompassing both traditional and contemporary folk music. The term originated in the 19th century but is often applied to music that is older than that. 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. It has been contrasted with commercial and classical styles. This music is also referred to as traditional music and, in US, as "roots music".

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. The most common name for this new form of music is also "folk music", but is often called "contemporary folk music" or "folk revival music" to make the distinction. This type of folk music also includes fusion genres such as folk rock, electric folk, and others. Certain types of folk music are also sometimes called world music. While contemporary folk music is a genre generally distinct from traditional folk music, it often shares the same English name, performers and venues as traditional folk music; even individual songs may be a blend of the two.