BIOS stands for Basic Input/Output System. It’s the firmware that starts a computer, checks basic hardware, and hands control to the operating system when you power on.

Why UEFI replaced it

UEFI replaced BIOS because BIOS had grown too limited for modern hardware. UEFI supports larger drives, faster startup, more flexible hardware support, and stronger security features like Secure Boot.

Simple breakdown

  • BIOS is older, simpler startup firmware for PCs.
  • It was built for much smaller, less complex computers.
  • UEFI is the newer standard that does the same job, but with better speed, security, and compatibility.
  • UEFI also works well with GPT, which supports much larger storage devices than the old BIOS-plus-MBR setup.

In plain words

Think of BIOS as the old-school starter system for a computer, and UEFI as the modern upgrade. The main reason for the switch was that computers outgrew BIOS’s limits.

TL;DR

BIOS = old startup firmware. UEFI replaced it because it is faster, safer, and better suited to modern PCs.