Carl Jung, a Swiss psychiatrist and psychoanalyst, wrote extensively about the different levels of consciousness.
The conscious mind is what you are aware of thinking or feeling on a daily basis represented by the tip of the iceberg. This is what most of us would consider the mind.
The subconscious contains information that can trigger our conscious mind to react in certain ways represented as the layer of the iceberg just below the surface of the water. Dream journals, Craniosacral Therapy, hypnosis, meditation, and taking plant essences are ways of connecting to your subconscious.
The conscious and subconscious mind are unique to each individual while the collective unconscious is information shared within the human species, represented by the largest part of the iceberg deep within the water. Carl Jung wrote about how archetypes fit into the collective unconscious.