Dreams are a communication of body, mind and spirit in a symbolic communicative environmental state of being. Our brains are in constant activity. Different states of consciousness (like awake, asleep, alert, drowsy, excited, bored, concentrating or daydreaming) cause different brain wave activity. Our conscience mind, or the part we think with, our "window" into life, only takes up a very small portion of our brain activity. Other areas control things like breathing, heartbeat, converting light to vision, sound to hearing, balance when we walk, etc. etc. Another area controls imagination. This area is widely an undiscovered frontier. Imagination is more then dreaming of a new car. When you look at clouds and see shapes, or wood grain and see images, this is the "order from chaos" part of your imagination. The mind cannot deal with chaos very well, in fact it will resist it and sometimes manufacture order. Then there is memory.
And then there is the activity called dreaming. I think that to accretion extent, we dream all the time. Even while awake! But the process is functioning in our subconscious mind, out of view from our "window". If defined precisely, they may not be referred to as dreams technically, but the activity is very closely related. During certain cycles of brain activity while asleep, we can "view" these dreams with our conscience mind and record them in our memory. (this is why we sometimes remember them).
Fine, but what are dreams? Well, with the above kept in mind (especially the order from chaos part) try to imagine this.; Your brain mind and spirit, while at rest "review" and analysis in it's own way long term, short term and spirit memory. It kicks around emotions, thoughts, ideas, actions and interactions of the short term memory. It has in it's background the trends of your life and philosophy to influence it. Your mind is also processing spiritual data, your beliefs, whether or not you violated them, your information gained through psychic intuition (we ALL have this to a certain degree) and of course, any communication from God. ALL THIS data, as well as your subconscious "reading between the lines" of what people do and tell you, is then processed unsupervised by you! All this data is a form of chaos, and your mind (like seeing images in wood grain or clouds) puts it all together in a form of visual "screenplay", a medley of sight, sound, emotion and imagined interactivity. The end result is.... You guessed it, a dream!
Ahh, but would it not be nice if it were that simple! Dreams are easily influenced by factors in your life and spirit, and these influences create "categories" that are almost infinite. We do broadly categorize them in terms like "prophetic, standard, physical and nightmare" (to name just a few) And these we study each their own, in order to gain benefit from them. I look at it this way: Our mind and spirit together with our brain, is actually the greatest computer ever devised! To understand it's "back of the house" processing is to learn more about ourselves, God, our future and each other. Many things can be gained from dreams, better health (mental and physical), entertainment and even financial gain! (dreaming of a invention or idea) Now that you know some of the basics about dreaming and what (theoretically) dreams are you should have a better grasp on how to understand and use your dreams.