h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

What exactly are dreams? I think the dictionaries say that they're subconcsious thoughts generated by an overactive mind...or something to that effect. Some say they're what you really want. If that's the case then I'm in big trouble. Some say they are the manifestations of our inner desires...which I guess could be true. I mean we all dream about being rich, or scoring with that person that seems unatainable, right? But then, how do you explain the ever popular naked in public dreams? Or how about the nightmares? I shudder at the thought.
Recently I wondered if it were possible to become addicted to sleeping. I should have been more clear in that I ment addicted to dreaming. When you're poor, dreams of unending wealth can really be stimulating. If you're a weakling, dreams of being the big, bad-a@@ could appeal to you. If you're not getting any (which I have recently dealt with) dreams of sex can REALLY be enticing. Especially if they're with different people. Basically you're fantisies. Now, honestly, who WOULDN'T want those kind of dreams??
What ARE dreams? Why do we dream such weird things, scary things, wonderous things, and inspiring things? What part of our brain registers that "hey, body's asleep, lets go play!" And then there are the people who have the power to control them. I've hit upon this once or twice. A truly wonderous experience if I do say so. Like living your life exactly how you want it. Vivid dreams so real you're confused when you wake up, or terrified of stepping out of bed lest something grab you...yet you KNOW it isn't real...
What was God thinking when he said, "Let man dream". Not a direct quote, obviously. But these mysterious pictures can be addictive. Like a new story each night and you wonder what it will be about and how it will end...if it has time to end before the alarm goes off or the sun wakes you.

What are they?