Shneiky :
Could you give us more information. Like do you have motherboard, and if you have what brand/model is it? Do you have a video card? And if you have, what brand/model is it?
+1. Where you're buying, as well. $ is the currency symbol for a lot of countries, and even ruling out the unlikely ones, you could be from Canada, Australia, New Zealand, or the USA, all of which have very different prices.
To answer the question, however, overclocking is the process of increasing the clocks on your CPU (though you can overclock your CPU, RAM, or even your monitor if you for some reason wanted to). Its primary advantage is increasing performance, at the cost of increasing heat and potentially even lowering performance or damaging your hardware if you do it incorrectly.