does anybody actually know [/b]why we dream? not how, but why.
there are many theoreys.
physiological theory is that we dream to keep the synapse exercised. 
psychological theoreys revolve around emotional responses to our past RL experience, transformed into the metophorical messages we see as dreams 
or if you look at the thread on " isnt this why we are here " you will get my sloppy perspective. 
To “renew our life source.”
In a Scientific perspective, it’s to “exercise the brain.” This is illogical IMO since the Brain recieves all the exercise it can handle during waking states. Sleep would then be a time for the brain to rest, but it doens’t seem to.
Spiritual perspectives and my personal perspective is that Dreams are visitations to our true reality and real places (“real” CAN be subjective in this case.) It’s said that if someone goes without REM sleep for more than 5 days or so, they go absolutely mental and unable to function. I feel this is because we NEED to contact that Source from where we come from, the same source that somehow keeps your heart beating every second of every day.
Quantum Physics states that since Matter must be observed to appear, then everything exists in potential states and the perception of that potential state creates ‘reality.’ This can lead to the idea that everything that CAN happen, DOES happen. Dreams are experiences of the infinite multitude of choices we could have made and experiences we could have had, but speaks to us in a language that most do not understand (that of the inner soul). Once we learn how to ‘de-crypt’ these messages, it usually leads to insight and discovery of ourselves. To me, Dreams are the other lives we live, giving us brief glimpses of the Eternal Life we’ve already, and have yet, to live.
In another topic somebody said, that mammals, birds and high reptiles only can dream, animals that are more primitive cannot. But they, as far as I can remember, are also creatures, which can have associations. So, maybe, the ability to dream is somehow connected with the possibility to form associations… 
An association is a sort of link between two ideas, it is like a conditional reflex, but deals with things that doesn’t seem to be important in the moment of remembering. A reflex forms when, for example, you give some food to an animal every time you switch on a lamp, and the animal remembers, that the light comes before the food. And not only a dog (for example) but also a bird, a lizard, a fish, any animal more complicated than a worm can have conditional reflexes. A reflex means only remembering important things, for example, getting food is important, so you will unintentionally remember everything connected with the food. But if you play a sound before switching the light, without including food or anything connected with food and other important things, a fish won’t notice it, but a dog will, and it will be an association, not a reflex.
Associations are more “progressive” than reflexes, because you never know what will become important tomorrow. But they also need much more brain activity, because now you have to process lots of stuff you will very likely never use. And, maybe, REM sleep is the time when associations are formed. In day-time the brain is busy thinking about important things, and at night it has also time to remember all the “noise” we have unconsciously perceived during the day and reprocess it somehow. Small children spend more time in REM, and they are also humans with very little experience and very few things already marked as “important”, and in fantastically short time they form enough associations to learn to speak, for example.
Though I am not sure, if dreams appeared to support the already existing ability to create associations, or they first gave a chance for the brain to use the time of sleep… I am not even sure, if dreams and associations are connected at all 
, but it seems to be very likely.
I think we dream to show our hidden emotions. Ive found before that if something if bothering me, but I dont know what it is, it will sometimes show up in a dream. Your subcontious (wrong spelling!) sees things that your contious (wrong spelling!) doesn’t, so It shows you in a dream. I think every dream has a meaning or they are trying to tell you something that you didnt notice. Its finding out what the meaning is or what they are telling you that is the problem!
Although some dreams may be totally random!!
They must be triggered of by something tho…
Thats what I think anyway!! 
Just a list of some theories I’ve heard of.
- Wish fulfillment (Freudian type)
- Dealing with personal issues
- Strengthening important associations and getting rid of useless ones
- Keeps our eyes moving so we can get air into them during sleep
egotripping, you think that a dream is real??
IMHO i think dreams show random event with issues that your subconcious knows about.