Well I'm going to be doing my first OC soon, and, at first, it really confused me! 
Nevertheless, I finally managed to get my head around it, by thinking the CPU is like a runner. Let me explain.
A CPU at stock speeds is like the runner jogging. When you increase the FSB, your runner starts to sprint. If you don't provide him with enough carbohydrates, or volts for the CPU, he will stop running. Also, if his body gets too hot, then it will shut down, much like your processor.
Personally for a complete beginner at over clocking, this will help to explain how it works; it certainly did for me! What does everyone think?

Nevertheless, I finally managed to get my head around it, by thinking the CPU is like a runner. Let me explain.
A CPU at stock speeds is like the runner jogging. When you increase the FSB, your runner starts to sprint. If you don't provide him with enough carbohydrates, or volts for the CPU, he will stop running. Also, if his body gets too hot, then it will shut down, much like your processor.
Personally for a complete beginner at over clocking, this will help to explain how it works; it certainly did for me! What does everyone think?