This term refers both to
American artists- Bob Dylan, The Byrds, The Mamas And The Papas- who electrified the previously acoustic protest genre, and a largely English fusion of Rock and traditional music.
Davey Graham, Pentangle and Ashley Hutchings- founder of Fairport Convention, Steeleye Span and The Albion Band- can be credited with defining and popularizing the British brand of Folk Rock and with influencing Led Zeppelin, Jethro Tull and Wishbone Ash.