Well, that is much easier to do. Laptops are so finicky about new processors.
Same as laptops when upgrading desktops. you need to find the right sockets that are compatible with your BIOS.
CPUID is is a good third party software that tells you all of this.
How to upgrade your processor on a desktop:
http://www.pcadvisor.co.uk/how-to/pc-components/3298873/how-to-upgrade-a-pcs-processor/
You were asking what BIOS is.
BIOS. Short for Basic Input/Output System, the BIOS is a chip located on all motherboards that contain instructions and setup for how your system should boot and how it operates. The BIOS includes instructions on how to load basic computer hardware and includes a test referred to as a POST (Power On Self Test) that helps verify the computer meets requirements to boot up properly. If the computer does not pass the POST, you will receive a combination of beeps indicating what is malfunctioning within the computer.