What Causes Creaking In Joints?

In the past few weeks or so, I have noticed an increased amount of my joints to be creaking or snapping. I am not sure if this is something to be alarmed of or not.. the thing that really bothers me is that my jaw has started to creak a little bit too, sometimes when I talk or yawn. I'm fifteen years old.. I thought that's a rather young age to be having joint problems? What could this be?