No one knows exactly what dreaming is or why it happens, but there are a number of theories about what dreams are. These include:
Dreams are messages from gods or spirits, or those who have passed on from life on earth. The dream might be a way for loved ones to communicate with you, or a message or warning from divine beings.
Some dreams are thought to predict the future.
The brain is sorting out information, rather like what happens when you defragment your computer’s hard drive.
The subconscious brain is trying to tell the conscious brain something. For instance, you dream about being in the snow, only to wake up and find that you really are cold because you have thrown the blankets on the floor.
Dreams might be a way of problem solving. Even after we stop actively thinking about a problem, the subconscious brain often continues to look for the solution, and sometimes the answer to the problem appears in a dream
Why do dreams occur?
The purpose of dreams cannot be truly answered until it is determined what a dream is. Since there are more than one type of dream, perhaps there is more than one reason for their occurrence.
For instance, it is knowns that some dreams are influenced by the physical situation the body is in while the story unfolds, and so this would seem that the subconscious is making the conscious brain aware of this. An example of this could be the way that a telephone will ring in a dream, even when it is totally inappropriate for this to happen. You are out in the middle of the ocean, and suddenly a telephone is ringing in your dream. You are not surprised by the telephone ringing because the dream story adapts to this new scenario immediately. Then if the ringing continues, you wake up realising that it is actually your real house phone that is making the noise, and not the one in the ocean.
It is thought by some that the subjects of dreams are symbolic rather than the story itself having significance. However, this interpretation varies from culture to culture and even person to person. For example, dreaming of flying could be said to mean that you are liberating yourself of a problem, and feeling good about this, or it might mean that you are getting above yourself and are heading for a fall.
Dream interpretation was taken so seriously by the early Greeks that special temples were erected for people to sleep in. Because it was thought that dreams were messages from Gods, special priests were employed to interpret the dreams.
Other temples were erected for Asklepios, the God of Medicine, and sick people slept there overnight, hoping that they would either dream of medical advice or even be operated on by Asklepios while they slept. On waking in the morning the sick person would report their dreams to the priest for interpretation and instruction. It seems likely that these people were given opium before they went to sleep, and that some of them were indeed operated on during their drug-induced sleep because reports of operations have been found.
Dreams can be influenced by external circumstances, and also by thoughts of problems that have been playing on your mind. For instance if a single woman sleeps with a slice of wedding cake under his pillow, it is said that she will dream of her future husband.
While most dreams are like being in a movie where the dreamer does not appear to have any prior awareness or influence over the story, some dreams are partially controlled by the person who is aware that he or she is dreaming. These are called lucid dreams. Perhaps the only reasons for these dreams to occur are to entertain, or to try out something in your imagination, like you do with a daydream.