The personal unconscious was the accumulation of experiences from a person's lifetime that could not be consciously recalled.
The collective unconscious, on the other hand, was a sort of universal inheritance of human beings, a "species memory" passed on to each of us, not unlike the motor programs and instincts of other animals.
The collective unconscious was expressed through 'archetypes', universal thought-forms or mental images that influenced an individual's feelings and action.
alchemy