The BIOS setup program - an acronym for Basic Input/Output System - is a currently vital part of a PC's system, without which nothing can work. The standard BIOS that has been in existence for decades. It configures the PC's hardware so that the operating system (Windows, Linux, OS X, etc.) can recognise all of it and install the appropriate software device drivers. The program itself is stored in a CMOS flash memory chip on the motherboard and it can be upgraded by reflashing the memory chip with the update according to predetermined procedures. However, it is being replaced by a mouse-driven Extensible Firmware Interface (EFI) BIOS.
An EFI BIOS can do far more than a standard BIOS, such as providing overclocking, and the mouse/laptop touchpad can be used to access and navigate through its sections. The keyboard had to be used to navigate a standard BIOS. An EFI BIOS is accessed at startup in the same way as a standard BIOS - by pressing a key (Del, F1, etc.) provided on the first boot screen in a message that reads something like: Press the Del key to enter Setup.
A particular make/model of motherboard's user manual has a section devoted to the BIOS that describes the features and settings. The manual comes with a new motherboard or can be downloaded (usually in the PDF format) from the manufacturer's website by searching for that model of motherboard's support page.
The image below is of an EFI BIOS used by an MSI motherboard that was current in May 2011, which also provides overclocking, games and utilities. The main settings are accessed by click