Folk can mean:

• a specific people, tribe, or nation
• folklore, stories and traditions told orally.
• folk art, art done in traditional styles

In music:

• folk music or folksong, music by and of the common people.
• folk dance, a 19th century form of dance
• folk-punk, a genre of music that combines elements of folk and punk rock music
• folk-rock, a kind of music that is folk music and Rock and Roll mixed together.
• folk metal, a sub-genre of heavy metal that mixes it with folk music