Bob Dylan is an American singer-songwriter. Described as one of the greatest songwriters of all time, Dylan has been a major figure in popular culture over his 68-year career. With an estimated 125 million records sold worldwide, he is one of the best-selling musicians. Dylan added increasingly sophisticated lyrical techniques to the folk music of the early 1960s, infusing it "with the intellectualism of classic literature and poetry". His lyrics incorporated political, social, and philosophical influences, defying pop music conventions and appealing to the burgeoning counterculture.