According to Freud, there are different layers or levels of human consciousness. At the surface (or top-level) is the conscious; just below this is the preconscious, and at the very bottom is unconscious. We may define the unconscious; the deepest level of consciousness, as a pool of unwanted or unacceptable ideas, wishes or desires, memories, and emotions. These unwanted things are pushed down into the unconscious so that we do not have to deal with them and so they do not interfere or cause problems in our daily lives.
However, they can be traumatic if they surface and enter either the preconscious or the subconscious. For example, Freud believed that people often have horrifically sexual fantasies that are so difficult to accept and deal with (and considered wrong within the boundaries of a moral society) that they are hidden away in the unconscious so that we don’t think about them and feel bad every day. However, if these fantasies rise to a higher level of consciousness it could result in us feeling ashamed and having emotional problems, or we could act out these fantasies and commit horrible acts.