Dreams/Daydreams

What are they exactly? Are they figments pieced together in our minds? Or do our brains get bored and make stuff up? They do tend to be off topic of your life sometimes, but mostly they reflect on what you did at some point in your life. And on the subject of the off topic ones, they don't make sense when you wake up, but they do when you live them.

Any other ideas?

I will attempt to speak science...sortta:

Dreams are needed to get a full restful sleep. Because when REM sleep occurs, you dream regardless of weather or not you remember it in the end. I guess it's the body's way of keeping the mind working, even in a state of full rest.

My dreams are beyond messed up but I think it's the brains daily excersices but you can also provoke dreams with prethought images or sounds, I think.