WHAT THE HECK IS THE 'BIOS'?
I have heard it called "Basic Input Output System" and "Binary Input Output System". BIOS is intended to provide the basic input/output services between the computer's disks, card slots and controller chipsets at bootstrap and to enable the computer to find an operating system from a 'boot disk'.
BIOS makes it possible to boot up the computer hardware, load the operating system from the hard disk, and get the machine running. The BIOS is stored on what is called an Eraseable Programmable Read Only Memory (EPROM). What this means is that the EPROM is a piece of silicon and copper that can store the BIOS program, and can be read at bootstrap. It can also be upgraded by 'flashing' the chip with new code.
BIOS SETTINGS
Your BIOS controls the bootstrap and initialization of all devices connected to the mainboard, including all memory, processors and controller chipsets on the mainboard. The BIOS is a program that has a user interface. You can access the BIOS user interface by pressing a control sequence of characters on the keyboard at some point.
Once in the BIOS, you can configure disk drives, memory, processor, energy saver settings, I/O registers and other settings, including some built in components in the mainboard.
FLASHING YOUR BIOS
These days the BIOS is stored on an 'Erasable Programmable' chip. This chip can be 'flashed' with a new version of the BIOS program to update it. Flashing is the process of loading a new version of the BIOS into the chip and then turning the voltage up on the chip momentarilly to 'burn in' or 'flash' the new program. This is all done automatically from software.
All BIOS updates and the flash utility should be downloaded from the website of your mainboard's manufacturer, as many makers customize or optimize (read: 'gratuitously tweak') the BIOS to match the configuration of their mainboard's chipsets.
IMPORTANT NOTE: YOU SHOULD ONLY FLASH YOUR BIOS IF YOU ARE EXPERIENCING PROBLEMS THAT THE MAINBOARD MANUFACTURER IS RECOMMENDING A BIOS UPDATE TO CORRECT.
If the update process to flash the BIOS to it's new version goes horribly wrong, it will turn your PC into a big paperweight, and render it totally useless. Flashing the BIOS should not be attempted by novice computer users.
BIOS TYPES
All BIOS perform Power-On Self Tests (POST), and if some part of the test fails, a 'POST CODE' is generated and printed to the screen in most cases. In addition, a BEEP sound is heard out of the PC speaker (if the speaker is plugged in). The pattern of BEEPS also can indicate what type of failure occurred.