It was a song and a dance performed together by Daddy Rice and several imitators such as Geo. W. Dixon and Bob Farrell. It was a big deal, kinda like when MJ did the moonwalk. For the "supposed" origin and background of this song see Nevin's article on Stephen Foster in Atlantic Monthly Nov. 1867 (20:608)which has been quoted and reprinted by just about everybody who writes about this subject. There are lots of versions- many verses most all starting with "Come listen all you gals and boys I'm come from Tuckahoe, I'm gwine to sing a little song, My name's Jim Crow. Wheel about and Turn about et&..."