C & Q lowers the frequency of the CPU @ 3 different modes depending on workload
Take for example a Athlon 64 3200+, it's operating frequencies are 800 MHz, 1800 MHz, & 2000MHz and therefore the benefits of it would be lowered CPU temps and energy consumption when the full processing power of the cpu isn't needed.
It's usually enabled via the BIOS & by setting power management settings in windows to "minimal power management".
On Another Note: you may or may not have to install Athlon 64 drivers/C&Q software if applicable.