What doe it mean? "collective unconscious"?

This term is from the texts of psychologist Carl Jung, who was a follower of Freud (founder of psychoysis). It refers to the shared fears, desires, and other "major themes" between all peoples despite language, geography, and other surface differences. E.g. Jungian thought holds that all peoples share a fight or flight response to fear based on the ancient and shared experiences of running from predators.