Great question, Daniel, thanks for inviting me! Great answers too...looks like some wise people were attracted to this one. 
I believe that there are different types of dreams. Some of them are prophetic, some are for teaching and some are what I would call traveling "dreams". The prophetic ones are views that either we see or that are given to us about that which will happen. For instance, I am sure many people had foreshadowing dreams, whether they realized it or not, about 9/11. Teaching dreams are connections to the Divine, as Theresa mentioned, in different forms, for learning and guidance. Traveling dreams are not really dreams in the sense that we talk about them, but, a non corporeal reality. They are periods of time where our spirit roams free, for all different reasons, although still connected to the physical body.