https://www.cnx-software.com/2011/08/22/bootloader-to-os-with-unified-extensible-firmware-interface-uefi/?amp=1
Unified Extensible Firmware Interface (UEFI) is a specification detailing an interface that helps hand off control of the system for the pre-boot
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https://www.techtarget.com/whatis/definition/Unified-Extensible-Firmware-Interface-UEFI
Get the latest info on UEFI -- Unified Extensible Firmware Interface -- the specification, why it's set to replace BIOS, advantages and disadvantages, etc.
extensible firmware interfaceunifieduefidefinition