Hello and welcome to the forums
From what I can gather from your post you are looking for an explanation of what RAM and CPU levels reflect.
Your CPU usage is how much of your CPU is being utilised at any given time to accomplish the tasks you have set it (plus just running Windows taxes it quite a bit); the higher the percentage the more your computer is doing, you should notice a drop in performance until you hit 99-100% CPU usage at which point your computer will most likely just stop dead temporarily while it tries to catch up.
Your RAM (Random Access Memory), is what Windows uses to store information which it may need at short notice. Every program takes up an amount of RAM and as long as you don't open or close any programs this level will be more or less maintained. As I say Windows uses a fair bit of RAM its self to render the desktop etc.
If you're looking to speed up your system take a look at this tutorial, it's been on the front page of the tutorial section of Seven Forums since forever. Optimize Windows 7
Follow some of the tips; although some of them just make Windows 7 loose some of its eye candy and shinyness but will improve your PC's response times etc.
I hope this helps, if you have any questions don't hesitate to ask. (Please note that my explanation of RAM and CPU usage is very, very, very basic)
EDIT: Dang Brink beet me too it!