im a moderator on one of the largest overclocking websites and forums on the net (overclockers.com and ocforums.com)

As stated its basically the art of making a computer run faster than it is supposed to. It is similar to modifying a vehicle in as much as to do it right and to get it to hold together is not cheap.

Ive been clocking now for 14 years and started because I could not afford a PC fast enough as I would have liked, back in the day computers were very expensive.
Now computers are as cheap as toasters the need to overclock has rather deminished and as such I now have many systems which have the power I require that are not overclocked.

Having said that however I do still own a overvolted, refrigerated system with very high performance quality components with a processor speed of 5ghz... its not needed though to be honest