Unified Extensible Firmware Interface (UEFI)
Definition - What does Unified Extensible Firmware Interface (UEFI) mean?
The Unified Extensible Firmware Interface (UEFI) specification provides and defines a software interface that is between firmware and an operating system (OS). UEFI replaces BIOS, enhances the Extensible Firmware Interface (EFI) and provides an operational environment for OS and boot-time applications and services.
UEFI is the default interface of all computers/devices pre-installed and shipped with Windows 8.
Techopedia explains Unified Extensible Firmware Interface (UEFI)
UEFI works like BIOS, but with enhanced control, security and manageability of the system booting process. UEFI is programmable and allows for the addition of boot-time applications and services by original equipment manufacturer (OEM) developers.
The UEFI implementation of Windows 8 provides secure boot services that prevent the loading of malware into the rootkit by evaluating and authenticating the certificate of each boot loader driver from the UEFI firmware that is stored on the system's motherboard. Thus, only UEFI certified applications and services can execute on boot.
UEFI is also implemented directly on the OS to only authenticate operating systems that are digitally signed.