Get something like CPU-z. Run it, and notice your CPU is apparently only 1Ghz or something(assuming stock HTT of 200), and is using low voltage.
CnQ does what it says on that wiki, unsurprisingly, lowers multiplier and CPU voltage when you aren't using the CPU much, which makes it cooler, and use less power. If you're overclocking, most people advise against it, as some people experience problems with voltages and the like. It's definately worthwhile if you're after quietness and especially if you have a temperature sensitive CPU fan. But if you're going to OC, it's probably one of the first things you'll be told to turn off.