What Is BIOS? How Its Works.

                       What Is BIOS?

Your computer’s BIOS is the first thing that loads when you start your computer. It initializes your hardware before booting an operating system from your hard drive or another device. Many low-level system settings are only available in your BIOS.
Modern computers predominantly ship with UEFI firmware, which is the successor to the traditional BIOS. But UEFI firmware and the BIOS are fairly similar. We’ve even seen modern PCs refer to their UEFI firmware settings screen as the “BIOS”.
BIOS and UEFI Explained

BIOS stands for “Basic Input/Output System”, and is a type of firmware stored on a chip on your motherboard. When you start your computer, the computers boots the BIOS, which configures your hardware before handing off to a boot device (usually your hard drive).

UEFI stands for “Unified Extensible Firmware Interface”. It’s the successor to the traditional BIOS. UEFI offers support for boot volumes over 2 TB in size, support for more than four partitions on a drive, faster booting, and enables more modern features. For example, only systems with UEFI firmware support Secure Boot to secure the boot process against rootkits.

Whether your computer has a BIOS or UEFI firmware doesn’t matter much in most situations. Both are low-level software that starts when you boot your PC and sets things up. Both offer interfaces you can access to change a variety of system settings. For example, you can modify your boot order, tweak overclocking options, lock down your computer with a boot password, enable virtualization hardware support, and tweak other low-level features.