The BIOS is software stored on the motherboard that initializes hardware and boots the operating system. It executes immediately after turning the computer on. To access the BIOS settings, the user presses a key like Delete or F2 during startup. This interrupts the normal boot process and displays the BIOS menu, allowing adjustments to hardware settings. Commonly the key to access the BIOS is shown briefly during early startup.

1.
How to access the BIOS ?
The BIOS or Basic Input Output System refers to a software program
that is stored in a permanent memory (ROM) on the motherboard of a
PC. BIOS is executed immediately after switching on the system. The
BIOS software, also known as firmware, fits exactly to the actual
motherboard and is therefore not simply interchangeable. One of the
BIOS tasks is to initialize all the existing hardware of a PC and then start
the operating system.
Initializing of the hardware is done by POST which stands for Power On
Self Test.
Each BIOS provides the ability to change certain settings on the
hardware. To make these adjustments, we must first enter the BIOS
itself.
Each BIOS manufacturer uses different key combinations for this
purpose. If these combinations are then held down for a moment right
after starting the computer, the BIOS then interrupts the normal boot
process and the BIOS menu will appear.
Commonly used keys or key combinations to access the BIOS are:
DEL ESC F1 F2 or F10
Here a tip: Just after the start of the system you will often see a small
message on the screen that shows you the exact key combination to
access your BIOS!
If you want to see and hear more about this: www.paulpaulito.com