By default the manufactorer might "lock" some features of a piece of hardware to make it have less preformance (but they also get to keep the same production sequence.) It'll save them some money, so they do it. By unlock, we mean to enable again. In most cases of Video Cards, by unlock we me re-enable a few of the pixel pipelines. Use Google and Wikipedia to learn more. To overclock is to set the Core Speed (the GPU's processr) and/or the Memory Speed to a level higher then the stock speed.
