Overclocking is the process of running a computer component at a higher clock rate than it was designed for or was specified by the manufacturer.
Clock Rate - Is the fundamental rate in cycles per second - measured in hertz - at which a computer performs its most basic operations.
FSB/HTT- FSB stands for Front Side Bus, and refers to the speed at which your processor can talk to your memory. In the AMD world, this is also referred to as HTT, which stands for Hyper-Transport Technology.
Multiplier - It denotes the speed with which the processor does its internal calculations. The multiplier is a way of describing the internal speed in relation to the FSB. So if the FSB is 200 and the multiplier is 10x, then the processor runs at 200 x 10 = 2000MHz or 2 GHz.
vCore - Is the voltage of the processor itself. As overclocks become unstable, you can use this setting to increase the processor voltage and make the chip more stable.
vDimm - Is the voltage of the memory. The memory can and often will be overclocked as well, and vDimm can be used to increase stability in ram.
Monitoring / Stability Testing – Tools such as Riva Tuner, CPU-Z, Speed Fan etc. allow you to monitor things like temperatures, voltages, fan speeds, clock speeds, memory settings, etc. Other software like Prime95 and SuperPi, stress-test the processor. These software give you the necessary feedback.
Cooling - Overclocking leads to high temperatures which must be managed. Extreme Over clockers rely on cooling systems to bring down the core temps. These systems include Liquid Nitrogen (LN2) and Water Cooling etc...