I'm Scott, and I'm an Overclocker. < Hi Scott! >
As pointed out, it's the act/art of telling your components that they're faster than they're actually supposed to go. Just that (only being electronics) they can't reason with us that they're not really 3.6 GHz, but in fact are supposed to be 2.4GHz. Instead, we tell them "You Are 3.6 Now. Go Forth and RUN!"
Since PCs are pretty literal about stuff like that, it goes "OK"
, and then tries to run however fast as we told it to. If the operator gives it parameters which are sustainable, then the processor will do what the operator says with little trouble. If Not.... then
Done Judiciously and Well, you can increase system performance for free and perhaps get a little more/better use out of aging components. Depending on the degree (not to mention the ability of the operator), it's also certainly possible to put a premature end to expensive components.
As pointed out a number of times: I/we strongly encourage to learn first, and screw with it later.