Dreams

I just got back from a weekend in Westport with the family and as I was laying on a beach way more beautiful than any Connecticut beach I've ever been to, this is what I was pondering.
I have this bookmark that my mom got me and on it, it says, "Believe in your dreams and anything is possible." We all know that those ideations we have and those things we aspire to, we call them dreams and talk about them as fantasies, but I got to thinking: what exactly ARE dreams? Don't get me wrong, I like a mystery of belief as much as the next person, but there are just so many possibilities here.
Let me precursor this whole topic by saying I'm a psychology major, so dreams and the mind are my "thing" through and through, but I'm also a Catholic who believes very strongly in my faith. It gets a bit dicey.
I know of two main explanations for what dreams really are. They come from the diciplines of science and faith; the two areas in which we all almost alway find ourselves spilt between.
In the world of science, dreams are easily explained. We all have an unconscious mind that we control, or at least keep at bay, when we are awake and alert. When we sleep and go into REM cycles, neurons starts firing like crazy and the unconscious becomes the context of our thoughts as we sleep, as we dream. Ramble, ramble, there's much more psychobabble, but that's most of it.
Now, in the world of faith and religion (or at least my own. I can't speak for anyone else's), the stuff of dreams is summed up in one sentence. They are messages from God that guide you through life. Be warned, just because this is a shorter explanation, doesn't mean it's any easier.
The question remains, where do I fall on this topic? How do I view dreams? The answer: I have no idea. I'm extremely torn in the world of dreams. I love them. I love the optimism of them, no matter which realm you view them from. I just don't know quite where I stand.
What I do know is this. If you don't have dreams, however you define them, it's a scary world...and an even scarier sleep. Obviously, we dream hundreds of times a night, but the mornings I wake up and can't remember any of them are some of my most annoying mornings. I view dreams as more pieces to fit in the puzzle of life. That includes the aspriations, hopes, and fantasties. They are the way to give me some answers that I just can't come across when I am awake and going about my day. If I didn't have them, I wouldn't have anything.
What do dreams mean to you? How do you define them?