Jung's theory divides the psyche into three parts. The first is the ego,which Jung identifies with the conscious mind. Closely related is the personal unconscious, which includes anything which is not presently conscious, but can be. The personal unconscious is like most people's understanding of the unconscious in that it includes both memories that are easily brought to mind and those that have been suppressed for some reason. But it does not include the instincts that Freud would have it include. But then Jung adds the part of the psyche that makes his theory stand out from all others: the collective unconscious. You could call it your "psychic inheritance." It is the reservoir of our experiences as a species, a kind of knowledge we are all born with. And yet we can never be directly conscious of it. It influences all of our experiences and behaviors, most especially the emotional ones, but we only know about it indirectly, by looking at those influences. The contents of the collective unconscious are called archetypes. Jung also called them dominants, imagos, mythological or primordial images, and a few other names, but archetypes seems to have won out over these. An archetype is an unlearned tendency to experience things in a certain way. There are some experiences that show the effects of the collective unconscious more clearly than others: The experiences of love at first sight, of deja vu (the feeling that you've been here before), and the immediate recognition of certain symbols and the meanings of certain myths, could all be understood as the sudden conjunction of our outer reality and the inner reality of the collective unconscious. A nice example that has been greatly discussed recently is the near-death experience. It seems that many people, of many different cultural backgrounds, find that they have very similar recollections when they are brought back from a close encounter with death. They speak of leaving their bodies, seeing their bodies and the events surrounding them clearly, of being pulled through a long tunnel towards a bright light, of seeing deceased relatives or religious figures waiting for them, and of their disappointment at having to leave this happy scene to return to their bodies. Perhaps we are all "built" to experience death in this fashion. So much for the content of the psyche. Now let's turn to the principles of its operation. Jung gives us three principles, beginning with the principle of opposites. Every wish immediately suggests its opposite. If I have a good thought, for example, I cannot help but have in me somewhere the opposite bad thought. In fact, it is a very basic point: In order to have a concept of good, you must have a concept of bad, just like you can't have up without down or black without white. The second principle is the principle of equivalence. The energy created from the opposition is "given" to both sides equally. So, when I held that baby bird in my hand, there was energy to go ahead and try to help it. But there is an equal amount of energy to go ahead and crush it. I tried to help the bird, so that energy went into the various behaviors involved in helping it. But what happens to the other energy? Well, that depends on your attitude towards the wish that you didn't fulfill. If you acknowledge it, face it, keep it available to the conscious mind, then the energy goes towards a general improvement of your psyche. You grow, in other words. But if you pretend that you never had that evil wish, if you deny and suppress it, the energy will go towards the development of a complex. The final principle is the principle of entropy. This is the tendency for oppositions to come together, and so for energy to decrease, over a person's lifetime. Jung borrowed the idea from physics, where entropy refers to the tendency of all physical systems to "run down," that is, for all energy to become evenly distributed. If you have, for example, a heat source in one corner of the room, the whole room will eventually be heated. When we are young, the opposites will tend to be extreme, and so we tend to have lots of energy. For example, adolescents tend to exaggerate male-female differences, with boys trying hard to be macho and girls trying equally hard to be feminine. And so their sexual activity is invested with great amounts of energy! Plus, adolescents often swing from one extreme to another, being wild and crazy one minute and finding religion the next. As we get older, most of us come to be more comfortable with our different facets. We are a bit less naively idealistic and recognize that we are all mixtures of good and bad. We are less threatened by the opposite sex within us and become more androgynous. Even physically, in old age, men and women become more alike. This process of rising above our opposites, of seeing both sides of who we are, is called transcendence. Jung also developed a personality typology that has become so popular that some people don't realize he did anything else! It begins with the distinction between introversion and extroversion. Introverts are people who prefer their internal world of thoughts, feelings, fantasies, dreams, and so on, while extroverts prefer the external world of things and people and activities. Read more about this on http://www.ship.edu/~cgboeree/jung.html