Blues is a particular kind of folk music, originating in the USA and arising from the work songs and spirituals of Americans of African descent. It is a simple music, often using only three chords, but in its simplicity is found endless variation. Blues became electrified after WWII and is alive and well today, while lyrically the form continues to offer players opportunities to explore the human condition. There is no doubt that having some familiarity with the giants of early blues－Robert Johnson, Muddy Waters, John Lee Hooker, Howlin' Wolf－will enhance appreciation of both modern blues-rock and indeed, the entire world of rock and roll.
Although each country has, by definition, its own folk music (thus, World music), the traditions of the UK (eg: Fairport Convention) and the US (eg: early Joan Baez) are those having the most influence on popular music.