Everyone has there own definitions of ghosts and spirits. And really no one is wrong. Webster's dictionary defines a ghost as "The spirit of a dead person which is believed to appear to or haunt living persons, a spirit." And defines a spirit as "The vital essence of man, considered by personality and self- consciousness, a supernatural being, as a ghost or angel. I don't know about you but these sound somewhat confusing.
I define a ghost as a person who has passed away but who has not crossed over into the spirit world. They are still Earth bound. I define a spirit as a person who has passed away and has crossed over into the spirit world. They also can cross into either world as they please.