CPU Scaling is a feature built into most modern (mobile) CPUs that allows them to scale up or down in how fast they run and how much energy they suck down based on demand. If you have a fairly modern mobile computer theres a very good chance that your CPU(s) can handle frequency scaling.
Read it at arsgeek
Why should you care? Well, you can control this to tell you computer how much power and how fast it should allow its CPU(s) to operate. This can save some energy and thus battery life at the expense of a little performance which is great for extending the use time of your laptop when its unplugged.