In my experience dreams can be any combination of a lot of different things. That said, I've heard the theory that REM dreams may not be anything at all, or that imagery is projected onto them upon waking, and as a lucid dreamer I find this nonsensical. Just my opinion.
I've found the most random or meaningless things don't happen during REM dreams but during hypnagogia or partial sleep. The other day I was about to take a nap, and I heard someone say "excuse me." There was no one there, obviously, but I almost turned around and screamed "WHAT?" I think it's safe to say there was nothing deep about that incident, just nonsense.
However, when it comes to REM dreams, I usually buy more into the Jungian approach. I am convinced that dreams are manifestations of the subconscious, including emotions that the dreamer has not worked out while awake. I've received spiritual guidance in dreams as well.
Weird. I've been having reoccurring dreams that I can only describe as a massive astral-based FPS game.