It’s very probable that in grade 9 you haven’t been introduced to enough math to fully use the mathutils module. I’m from the UK and am not familiar with US grades, but just googled and it seems you’re 14-15? In the UK education system, math students will start learning about vectors and matrices at around your age. If you look through your text books then you might well find that they contain information about vectors and matrices that you will be taught this year or next year. Quaternions are a completely different matter and usually aren’t taught until university level.

If you’re interested though then there’s nothing to stop you from learning what you need to know yourself. If you have a basic knowledge of algebra, trigonometry and locating points in space by using coordinates/vectors then you already know most of what you need to get started.

I’ve found that http://www.euclideanspace.com/maths/index.htm is a great reference for learning about 3d math. The whole site is very good at explaining all aspects of 3d world creation. Most of the information there is not directly relevant since it covers the creation of a 3d engine from scratch and most of the groundwork has been done for us by the nice Blender developers. All of the information will provide you with an understanding of what goes on behind the scenes though.

Wikipedia is also a good resource, although I find that the explanations there tend to be a bit more technical and harder to follow.

Math is somethimes hard to begin with, but if you learn how to use the functions in Blender then you will have a good basis for your learning and comprehension. Learning from using is far more fulfilling and interesting than learning from books where the uses are often ignored and make things boring. If you don’t want to wait for a few years then you’ll have to do a bit of reading yourself. Good luck in your learning.