Why do we dream, the things we dream?

My dreams are always so way out of here. I think it has to do a lot with my mind that never stops running and my crazy curiosity and creativity maybe?

I can have a full novel of a dream that revolves around a female with flaming red hair and the legs of a fawn. She may be asking me to do something or help her to a new town. We will have to use what is around us and build something to travel in. The other night it was that we need to fly over a field of razor sharp grass. Just a tiny touch would need stitches. We had to create something on the ground that would work to fly us over the grass safely. Now, this flaming red haired fawn girl is NO help. She just kind of paces back and forth crying. To confused to throw in Ideas. While I was out gathering leaves and sticks and bones from half eaten elephants. She would still be stressing and pacing while I was sitting sketching out my idea in the dirt with a pointy elephant bone. Bones were all that was really left. It's like the natives smell dead elephants and come and steal the tusks right away. I eventually build something sturdy enough to take us over and save the day. But I always wonder what these dreams mean. Why this fawn girl and I never become friends even though I am always helping her out.
I should really write these dreams down. One day I could possibly have a book of small stories.