Specification: UEFI
From wikinotes
The Unified Extensible Firmware Interface
Documentation
Official Spec https://uefi.org/specifications wikepedia https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
Tutorials
UEFI TLDR https://www.happyassassin.net/posts/2014/01/25/uefi-boot-how-does-that-actually-work-then/