UEFI is a modern replacement for the BIOS (Basic Input Output System). It was designed to overcome many limitations of the older BIOS standard, including:
- UEFI supports drive sizes upto 9 zettabytes, whereas BIOS only supports 2.2 terabytes.
- UEFI provides faster boot time.
- UEFI has discrete driver support, while BIOS has drive support stored in its ROM, so updating BIOS firmware is a bit difficult.
- UEFI offers security like “Secure Boot”, which prevents the computer from booting from unauthorized/unsigned applications. This helps in preventing rootkits, but also hampers dual-booting, as it treats other OS as unsigned applications. Currently, only Windows and Ubuntu are signed OS (let me know if I am wrong).
- UEFI runs in 32bit or 64bit mode, whereas BIOS runs in 16bit mode. So UEFI is able to provide a GUI (navigation with mouse) as opposed to BIOS which allows navigation only using the keyboard.