goku, vegeta, hercule and dende, who were like the only earthlings left alive got sent to the supreme kai's planet before Buu blew up the entire planet. buu then started looking for goku so he kept teleporting to abunch of different planets where he feels any sort of higher level people and blows up the whole planet. goku ends up luring buu to the kai planet. vegeta fights kid buu 1st, and gets beat and finally admits Goku is better than him. then goku fights him. they use the namek dragon balls to bring earth back and everyone who was killed and goku used everyones energy to make a spirit bomb and kills buu with it. the end and Hercule takes credit for beating Buu. and Buu is reincarnated as a good guy as a small indian looking guy named Uub.