Dreaming

What are dreams? I sit in bed every night, before I go to sleep, thinking about what world I'll be in when I go to sleep. What if dreams were real life, and what we think is real life, is actually, a dream? Are dreams what is going to happen in the future, and it's giving us a warning? Are they things that will never happen? Or just in fact, 2 words, a dream?
Dreams sometimes can link to actual real life sensations, such as the incorporation of environmental sounds into dreams such as hearing someone yell in a dream, while someone is actually yelling in reality... thats what makes them so life like. But the worst bit is, when you wake up from a great dream, and you realise it wasn't even real, and theres nothing you can do about it. But if you've had a terrible dream, waking up was the best part..
A situation I stumble across constantly, is de ja vu. I come across situations where I have most definatley had a dream about, and I know whats going to happen. I have to stand back and really think about it... it scares me a bit. I was thinking of this subject, just before I went to sleep. I can't remember my dreams very well, only if they are very signficant. I used to ask my archangels to give me messages through my dreams, and tell me what's going to happen with certain things... I got some answers, but how am I to be sure? Another question is, Are dreams messages from the other side, or is that just what we want to believe?...