Welcome to sketchup! You can google the heck out of this question, but the short answer is that if you are just starting out you want to be using sketchup 2016. Layout is for creating 2d documents out of your 3d models, and style builder is for customizing the “style” aspect of the way sketchup shows your drawing. It’s not that the other two are not useful it’s just that you are unlikely to use them until you have a better working knowledge of Sketchup, then their usefulness will make more sense.
start with sketchup, and good luck!