Dreams are what your brain does to prepare you for real life events and are also a product of thought. I had a dream about chameleons last night because I was stressed that my chameleon might die overnight ^^;. It all depends.
(I woke up and she's bright green, no sunken eyes, nice and healthy)
REM sleep and non REM sleep also help explain how we dream. I thhhiiink how it went was that the reason some people sleepwalk is because they're in REM sleep, the brain is playing through a possible chain of events and you are reacting to it in dream to 'prepare' you for real life events that may happen. Non REM sleep is probably just crazy nonsense. Kinda like taking LSD, but minus the LSD, haha.
I think all those horoscope/dream reader/crap is a bunch of asshair, honestly. :\