Dreams are very egalitarian. I really believe that one person knows just about as much about dreams as another person, since almost all of us do a lot of it, and no two theories about dreaming are the same. However, I would like to give you some of what I have learned from my own dreams and readings about them. In addition, I have included a reference that discusses Scientific dreams studies in some detail.

When I was about 14 years of age, and burning up with a desire to learn more about medicine, I bought the only “medical” book I could find in Grass Valley, California: The interpretation of dreams, by Sigmund Freud. I vividly remember being amazed at how Freud could figure out the symbolisms in the dream case studies he published. The interpretations were not at all clear to me, even after I was told the answer, and chewed on them a bit. I subsequently read the opinion that a lot of them were made up. The essence of Freuds theory of dreams is that they were wish fulfillments, which is patently not always true.

REM sleep was linked to dreams in 1953, a couple of years before I graduated from medical school. For years, dreams were studied in a unitary context of REM sleep, and in the opinion of some, this has slowed down progress on the knowledge of dreams immeasurably. We now know that dreams are not always linked to REM sleep. Dreaming can be neurologically interrupted, while REM sleep goes on. REM sleep can be eliminated while dreaming goes on.
So we go back to the starting block; what are dreams?
The Ancients put a lot of stock in dreams, such as Joseph’s dreams predicting a seven-year drought, which earned him a place on the pharaohs Staff. Martin Luther thought they were the work of the devil. My son Michael thinks they are a good thing, since when you dream you are sleeping, and sleep is a wonderful restorative.
My own theory is that they are random fragments of experience which are ordered and supplemented to form a story. These random fragments can either be from recent experiences, perhaps being consolidated in memory, or old experiences that are being pruned as unnecessary. These snippets are then aggregated under the influence of mood neurochemicals, and flow out in the dream narrative.
Sensations coming in from the environment can play a role. I will always remember the story of a sleep study patient, who was slapped on the back of his neck by a wet towel. He awakened immediately, and vividly remembered a dream about the French Revolution, in which he was guillotined. I read that dreams take 5 or10 minutes of time to develop, however.
I dream almost every night, and most are forgotten rapidly. Some have enough detail and meaning for me too mull over before I get up. Some of my more common dreams are of flying, or getting lost. The pleasant dreams are definitely in the majority. Only rarely, a sinister one will wake me up.
The following reference details about 50 of the most common dreams that people experience. Much other pertinent information is contained. What is your theory on the causes and meaning of dreams? You probably have as good an idea as anybody else.