FSB is your front side bus, this is the base speed of all components on your system. All other devices connected to your north bridge have a multipler of this value for their speed. (pci, pci-e, memory, cpu) As long as you know how to reset your motherboard bios (usually a jumper) increasing the FSB is a safe way to overclock your system, just start small and make small increases. Changing the voltage is for advanced overclocking and I woudln't recomend it unless you are willing to replace your hardware. Its quite easy to overvolt and fry your components.
As you stated you are a begginer, I would start by downloading Asus TurboV software and giving it a shot.