Dreams do have meaning, but not all dreams have significant meaning. Sigmund Freud published one of his most important works, The Interpretation of Dreams in 1899.
In it, he reveals much about the sub conscious, or unconscious. He finds that dreams largely represent wish fulfillment, repressed memories, and imagery that the dreamer may not be comfortable with on a conscious level. Freud believed, at least at first in his career, that many dreams images were sexual in nature. He posited that going up and down upon a ladder, or dreaming about a pump, for example represented the sexual act. In later years he changed his mind about such images. He still found much to be sexually revealing, especially of sexually repressed longings, which would have been socially unacceptable in Victorian times, but he also was open to much more general interpretation as well.
In the example of someone dreaming about a snake, there is always the possibility that the snake represents male sexual longing, but just as often it almost always is interrelated to be about energy and power, or a true phobia about snakes.
Suppressed longings may manifest in dreams in many kinds of imagery, not just as snakes, or trains, for instance, but things such as cables (a modern snake) or vines, forests and tunnels. Interpretation is also quite overwhelmingly dependent upon the feelings reported by the dreamer, his or her cultural background, his or her own views of the imagery in waking life and so on. If a woman who is deathly afraid of cupcakes for example, had a childhood trauma involving being burned by a stove when she reached for a cupcake at age six, this important information would be factored in when analyzing her dream. Yet inquires are also made about temptation, reward, and related ideas generally associated with “cupcake.”
Freud also wrote about psychic determinism. This idea was also based on the idea of hidden longing, and repressed thoughts. It says that an idea or image from a dream is largely determined by some daily connection to an everyday experience.
That is, the dreamer may make deliveries as part of their day time job, and when they dream about making an important presentation, say about dropping a clattering, silver tray to a king, the dreamer is tapping into his associative memory about presentation, delivery, insecurity and self consciousness about job performance. The idea of psychic determinism is basically that nothing we think of spontaneously is by accident alone, but is determined by our psychic associations.
Freud’s most critical contribution to the field of psychology was the idea of the unconscious. Whether he was correct that so much of the unconscious was based on our early childhood fears and repressions is still debated. His idea of finding how to learn more about the unconscious mind through free association, both in language, and in dream interpretation, is a fundamental key to psychoanalysis.
Biopsychology is the field of psychology that deals with our physiology, brain chemistry, and biological evolution. Because the medical aspect of Psychiatry was formulated out of the Freudian model (Freud was a medical doctor), Biopsychology studies not just sleep and dreams, but the neurotransmitters and hormones involved.
The newest branch of Psychology, Ecopsychology, deals with the current realization that human beings are evolved animals, just at studied in Biopsychology, but that they are also very literally totally dependent upon an environment for sustenance. Therefore, a dream of a waterfall could be associated with the idea that our bodies are at least 70% water, and our inter-dependence upon all living things encircled by the living body, and external to the living body, also are major factors in our humanity, and therefore the human psyche. Dreaming of suffocation may not just be about a person feeling overwhelmed by responsibility or obligations, but also with the physical reality of air quality in the external world.