If you have read Harry Potter you know that Harry killed Voldemort because Voldemort split his soul into 7 pieces so he could never die but he didn't know that Harry Potter was one of the pieces so when there was only one piece left he didn't know there were actually 2 : a snake and Harry Potter so when niville longbottoms killed the snake Harry Potter was last piece of Voldemort but again Voldemort did not know that so he killed Harry therefore killing him but Harry did not die because his mother lily potter had protection on Harry and Voldemort used avada kedarva so only killing the tiny piece of Voldemort that was in him.