The performances of your computer are limited to it’s hardware. Hardware is the componants of the computer such as the Hard drive, ventilator, graphic card, memory, cd/dvd player, monitor etc. These componants can only function at a certain speed, they are physical limited. However some of them have limiters set by the manufacturer, in order to not over head or malfunction. (The same applies to cars, some have speed limiters, the engine is physically capable of going faster but it is legally considered dangerous so limiters get fitted) You can download softwares which enable you to control the limits set. Down clocking is when you lower the limite, therefore the component will work slower, this works by changing the amout of electricity and energy the hardware gets. And over clocking is the opposite, you higher the limite, which will boost your computers performances. This is often done by gamers. Video games have great graphic designs, but to be in order to view these graphics at their full extent you need a good graphic card. And what gamers do is they manualy over clock the graphic card to make it work faster, therefore having a better game. However this can result in the hardware to malfunction, break or burn depending on how long and how much you over clock. The opposite scenario is also possible, some games have such high graphic levers that your graphic card overheats and then your computer doesnt work correctly. You can therefore lower the limit, which will prevent the component to over heat.

If you do manualy change such settings on your hardware you must be aware that you might break them. You must inform yourself and be aware of the risks. However they aren’t any risks of downclocking, because it basically just makes everything slightly slower, so nothing can over heat. People who overclock their components focus mainly processors, video cards, motherboard chipset and RAM, they do so because these are the components which define the “speed” of your computer.