There are many types of dreams, according to how you may classify them.  There are repetitive dreams or recurrent dreams.  Usually these carry a message that needs to be heeded or discovered.  The message can be repeated since you were a child, occasionally, once a month, or even every night! This can be an aspect of the personality or a problem that has followed you your lifetime.  Normally, when the key or message is discovered, the dream disappears.   Of course these can also represent a more current problem, preoccupation or subconscious fear.

Insight dreams, sometimes called explanatory dreaming, provide counseling, clarity, or resolution of important life issues affecting you.  These dreams can often occur during periods of inner turmoil, doubt, or despair providing some insight to situations that need to be explained or resolved. These can come as a series of dreams when the original dream's message is not understood.   They may also provide solutions in a way we are not able to consciously grasp to move us past blocks and preconceived notions that we are encountering with the conscious mind.

Lucid dreams are experienced while we are aware and seem so real.  Sometimes it is not realized that we are dreaming until we awaken!   This can often be a breakthrough dream experience revealing a consciousness that is awake and able to understand the dream state.  The dreamer awakens within the dream and controls events and the very direction of the dream.  Apparently, it is also a common experience involves feeling awake in bed with an intruder in the room.What is perceived to be an intruder, is really you! Lucid dreaming can be the spring board to out of body experiences and astral projection.  The lucid dream has been used by sages for the ages as a pathway to discover who you really are!

Precognitive dreams tap into your subconscious mind revealing the outcome of events before then occur.  This extraordinary ability is revealed in the language of the subconscious mind which is often metaphoric or symbolic rather than literal.

There is a dream type referred to as the review dream.  Life often changes how we view ourselves and review dreams reveal how we have evolved through these experiences. Since I have not found a literal example of this dream, I am unsure of how they occur or what the experience is like.  To me the review I have heard about reflecting your whole life and its changes is the one when you are dying!

Ohhhhhhh!  Gratification dreams!  We can't have everything we want so some dreams satisfy our unfulfilled desires.  We are fulfilling our desired through the experiences in our dreams, perhaps satiating desires that would otherwise get us into trouble.  I will leave the imagery up to your own mind, experience and age.  :-)

Physical dreams have lasting physical or emotion affects that we feel upon the waking state.  We wake up with pain, fear and even wonderful feeling such as joy!  The physical affect of these dreams cause us to review and evaluate their meaning.  This is a way dreaming captures the subconscious mind with an impression capturing the attention of the conscious mind. 

Nightmares can occur through many of the dream types.  These can be attention getting, repetitive, be part of a fear that remains in the subconscious, or the after affects of a great pepperoni pizza.  

Past life dreams are vivid dreaming representations that may seem out of place within the context of your current life.  It may even seem that it is not you!  These dreams tend to be less symbolic and easier to understand once they are identified.  These dreams can be another life time or from childhood times that have been forgotten. 

Astral projections are experienced as very realistic feeling, vivid, memorable, and colorful dreams.  The feeling of leaving the body occurs and often leads to a wonderful experience.  The person often returns feeling happy, rejuvenated, and much better for the experience.   Some have described the experience very differently and yet with positive outcomes.  Shelly Wu, PhD., speaks of what she calls a demon dream experience: 

"I will describe one instance of these dreams (March 30, 1907, in Berlin), following immediately after a lucid dream. The lucidity had not been very intense, and I had some doubts about my real condition. Then all at once I was in the middle of demons. Never before had I seen them so distinct, so impertinent, so aggressive. One was slippery, shining, limp and cold, like a living corpse. Another changed its face repeatedly and made the most incredible grimaces. One flew underneath me shouting an obscenity with a curious slang-word. I defended myself energetically, but principally with invectives, which I felt to be a weakness. I saw the words written.

The circle of demons was close to me and grinning like a mob of brutal street-boys. I was not afraid, however, and said: "Even if you conquer me, if God wills it I do not fear." Then they all cried together like a rabble, and one said: "Let God then speak first!" And then I thundered with all my might: "He has spoken long since!" And then I pointed at one of them, saying: "You I know for a long time!" and then pointing to another: "And you!"

Then I awoke at once, and I believe I made some audible sound in waking up in the middle of my apostrophe.

And then--this will astonish you most--after this dispute I felt thoroughly refreshed, cheered up and entirely serene and calm.

This is the principal difference from the symbolic dreams that in the demon-realms when I see the demons and fight them, the effect is thoroughly pleasing, refreshing and uplifting.

This is the principal point in these demon-dreams--that, whether these beings have a real existence or whether they are only creations of my fancy, to see them and to fight them takes away all their terror, all the uncanniness, the weirdness, of their tricks and pranks."

Dreaming has many purposes to assist us here.  They are the gateway to the spirit and to other worlds according to some.  At the very least, they are the window to the subconscious.  Explore your dreams to find what may be your inner Einstein, or your next beautiful creation!