"Unknown Dreams"
It's weird to think about isn't it? The way something so enchanting can be forgotten within a few seconds. But I guess that's just how dreams work... Right? How they can simply disappear right after you awake from that dark slumber. How they can be forgotten so easily.
That's what makes them "unknown". You don't know why they are here. You don't know why they even exist. Maybe, they are to help your mind sort out the memories of the day. Or--- they could be to warn you of upcoming events. But, we don't know. We don't know anything about what happens to us in the midst of these solemn nights where we rest. 
"Unknown Dreams". Such a simple but powerful term. Don't you think? Not only can it describe somebody's dreams--- but also themselves. Dreams. It's not only something that happens when you sleep, but it happens in the day as well. Dreams aren't just small fragments of our memory playing in our mind when we sleep. They are so much more. They could be the goal to open a café. Or to become a popular football player. 
Though sometimes, these dreams--- are not figured out. They hang in the air waiting for somebody, anything to grab a hold of them and keep holding on until that dream ends. 'Till that dream has faded and become a reality. 
"Unknown Dreams"
You've just gotta hold onto them until they are ready to become real.