Check the FAQ for some helpful stuff...
You might want to get SOME info about OCing and then come back and ask a more specific question
OCing is essentially making a part faster so it will perform better/similar to another, better part. Ex. OCing a AMD Barton 2500+ to 3200+ speeds.
Of course you always risk damaging a product by OCing and you might not be able to return it, but if you know what you're doing, OCing is very beneficial.
That wasn't too specific, but just use google and you should be able to find a lot of info.