Overclocking is when you go into your BIOS, and manually set the CPU frequency (FSB, QDR, QPI etc.) and if needed the core voltage. this usually results in the RAM being overclocked as well, unless you set the overclock mode to unlinked in the BIOS.
There's alot of info to get you started - and you can even search by your CPU model at Tom's Hardware Overclock section to gain some general as well as specific knowledge to your CPU.