Overclocking is a method used to push the performance of a computer's components-the CPU, the chipset, the RAM memory, and the graphics controller-beyond their rated limits in an attempt to make the system run better and faster than the designers' specifications. The most common techniques for overclocking include increasing the processor speed and increasing the system bus speed.
Depending on your point of view, you can think about overclocking as either the computer equivalent of fine-tuning a car to wring out every possible bit of performance, or as a somewhat obsessive practice that might cost more money on extra cooling and other components than it would cost to achieve the same performance with a faster processor.
In other words, overclocking is one of those activities that has less to do with using a computer as a tool for performing other work, and is more of an end in itself; most overclockers aren't concerned about making their computers work better for word processing or Web browsing, but they are delighted when they can increase the score that the computer achieves on some benchmark test of raw computing speed.
Overclocking is almost exclusively a sport for owners of desktop computers; the close quarters inside a laptop case make it almost impossible to increase the cooling needed by an overheated CPU.
Why would you want to overclock your computer? The most practical reason is to improve the performance of an older computer so that it can run newer games or applications that need more power than the computer was designed to provide. If you're on a very tight budget, overclocking might allow you to keep that old clunker in service until you can afford to replace it.
But for some people, that's less important than the simple challenge of pushing the CPU, motherboard, and other components to their absolute limits, and the opportunity to announce on an Internet newsgroup that you are running your system 37 percent faster than the processor's rated speed. And if you're an enthusiastic gamer, it's possible that even a tiny improvement in performance can make some of your games run noticeably better.
In the end, the best reason to try overclocking your computer is for the pure joy of the exercise, rather than any kind of practical application. If hot-rodding a computer sounds like fun, and you don't depend on that machine for reliable day-to-day use, go ahead and try it. But don't assume that you can just move a few jumpers on a motherboard and magically turn your antique computer into a rock-solid state-of-the-art screamer.