Well there is a lot of discussion about dreams but from what I know your brain dreams to help it lay down new memories of things you have taken in that day. Your brain get bombarded with information all the time and it is thought that sometimes it needs some quiet time to go through all of it and decide whether to file it away or just chuck it! So dreams start off in your left cerebral hemisphere as thoughts from the day (as your left brain is very logical and organised). Then as you go further into a dream your right brain takes over and starts having fun with the subject matter. Your right brain is very much more creative and flexible than your left, so the thoughts go from more sensible things to some of the wacky and wonderful things that can pop up in your dreams. So some dreams seem more real and that probably to do with what stage you are at in the dream and how close to the original thought you are. Think back to some of your dreams, did they start off quite normal and then spiral into silliness?
But on a serious note this is why it is so important to get enough sleep especially if you are learning, as your brain needs some downtime to process everything. If you spot animals or humans from going to sleep they will eventually die!!! Thats how important sleep is.
Somthink I was thingking recently is that it is almost amazing that dreams do not seem even more real. The brain is facinating. Our eyes dont see the world quite as we we see it in out head. Really your eyes could be considered quite simple if you comppare to the brain. The reason we see and feel and interprit the world is that the brain is processing the information we give it.
So if we fool our brain, like with a dream, then our conciousness has to basically assume it is true! Just a thought.