Types of Dreams

Dreams are a basic part of being human.  Everyone has them, and, on average, we spend about 6 years of our lives dreaming, according to HowStuffWorks.  Despite this, we don't know much about dreams and their functions.  Experts tend to be torn as to whether dreams are just the physiological firing of neurons or are actual psychological necessities, which allow us to work through personal issues.  There is a very robust market in dream interpretation that attempts to examine dreams according to various symbols and archetypes which show up in the dream itself.  For our purposes, we'll divide the dreams into Nightmares and Common type of dreams, and give a little information on both.

Common Dreams

Dreams occur most often during the REM (rapid eye movement) cycle of sleep, when our bodies are in their deepest stage of sleep.  Our bodies, at this time, are paralyzed by the brain.  So if you've ever tried to scream during a dream or do some drastic physical action and found that you couldn't, it's because your body has been paralyzed by your mind to prevent you from acting out the dream.  Among other things, sleepwalking can be caused by a deficiency of the chemical that paralyzes the body, though sleepwalking usually occurs in the earlier stages of sleep and not REM.  Here's a list of common dreams.  As I'm not a dream therapist, I won't be offering analyses.

False Awakening - A false awakening is when the dreamer, usually towards the end of the night, starts dreaming about going through their usual morning ritual.  Certain things will be out of place or unusual, and it's not uncommon for the dreamer to have several false awakenings before actually waking up.

School or Work in the Nude - In this dream, the dreamer is going about a normal routine and suddenly finds they are naked, usually in a crowd at work or school.

Falling - In this dream, the dreamer is falling off a cliff or out of a plane or somehow ended up in midair, and is falling towards the ground.  The usual tendency is to wake up immediately before hitting the ground.  Myth has it that if you hit the ground before waking up, you will die.  There is no way to prove this has ever happened, and some have reported hitting the ground and surviving.

Flying - Sometimes people will dream of having the ability to fly.  This could go in any number of directions.  It could just be flying around, or it could eventually evolve into a falling dream.

Teeth - There are a lot of dreams that involve teeth falling out or disintegrating.

Sleeptalking - Sleeptalking isn't technically a specific type of dream, but it is a common occurrence.  The sleeptalker, or somniloquist will start talking out loud during their sleep.  It could be in any number of forms.  They could just mutter a few quick phrases, they could just incoherently babble, or they could actually talk with an awake person.  Sometimes, it's just an example of a person breaking through the REM paralysis and speaking the words they're saying in the dream.

Nightmares

Most people have, at some point, had a nightmare.  A nightmare is an unpleasant type of dream that, when you wake up, causes some negative emotion such as fear.

Sleep Paralysis - As said before, during REM sleep, the brain paralyzes the body.  It is not uncommon to awaken from REM sleep and remain paralyzed to some extent.  This may be accompanied by hallucinations, which, since you are technically awake, is experienced as an especially terrifying dream.  It's often interpreted as some malevolent force paralyzing you or sitting on your chest, known as an "Old Hag Attack."  This can be common on airplanes or buses, if you aren't used to sleeping upright and are suddenly jerked awake by slight turbulence.

Night Terrors - Night terrors are characterized by intense fear and screaming, and are particularly unnerving for someone observing the night terror.  The person experiencing the night terror themselves can rarely remember it.  The subject will usually appear to wake up, screaming, and will have some difficulty being brought fully awake.  Cases have been known to last for 3 hours, but usually are just a few minutes.

Incubus/Succubus Attacks - These are particularly unpleasant dreams, and may or may not be part of sleep paralysis.  In these dreams, a demon rapes or has sex with the victim.  It is similar to the "Old Hag Attack" in that the victim experiences paralysis or something sitting on his or her chest, but it differs in its sexual connotations.  An incubus is the male form, a Succubus is the female form.

Lucid Dreaming

Lucid dreaming is when you know you are dreaming and then can potentially change the outcome of the dream by controlling the elements in your mind.  This is not uncommon, and people have been known to offer courses in how to lucid dream and then take control of that dream and have certain desirable things happen.  The best way of getting a lucid dream is by sleeping for 5 to 6 hours, waking, spending an hour awake and focusing for that entire hour on having a lucid dream upon going back to sleep, and then going back to sleep.

Another similar field is dream recall.  Dream recall is the practice of attempting to better remember the dreams one has.  Typically, a person has multiple dreams a night, but usually most of them are quickly forgotten upon waking.  Simply by writing down dreams immediately upon waking, one can remember the types of dreams they had and the content of those dreams.  As you do this practice more, you become better at remembering your dreams, and more likely to have lucid dreams.  It is also possible to focus ones intentions on having a specific dream, then going to sleep and having that dream.

Prophetic Dreams

Dreams that are prophetic or are perceived to be prophetic are not uncommon.  There is some skepticism around dream prophecy since, as we have many dreams at night, it's possibly coincidence that something that happens in a dream would happen in real life.  They do happen, however.  Joan of Arc and Abraham Lincoln famously dreamed their deaths shortly before they happened. 

Another aspect of this is that occasionally, flashes of insight or creativity come in dreams.  For example, Paul McCartney famously dreamt the tune to his classic "Yesterday" in a dream, and tried putting a number of words to it, such as "Scrambled Eggs," until he found the current lyrics.  Albert Einstein was inspired to think of the theory of relativity through a dream.

Dreams are universal, and are far too complex for our modern technology and psychology to totally understand, but there is an incredible amount of research being done on dreams as we speak.  So keep an eye out for better information coming out in the news in the near future.