is a firmware boot order
is an open standard independent of any programming language
is a version 2 variant of Extensible Firmware Interface (EFI)
encapsulates GRand Unified Bootloader (GRUB 2)
when a computer is booted, UEFI loads files stored on the EFI System Partition (ESP) to start installing operating systems and various utilities
UEFI was a direct replacement for BIOS, and whilst UEFI has been standard for over a decade, it's commonly referred to as BIOS

UEFI - Implementations