TLDR: The Unified Extensible Firmware Interface (UEFI) is a modern firmware standard introduced in 2005 to replace the legacy BIOS system. Designed to initialize hardware during boot and pass control to the operating system, UEFI provides advanced features like support for larger hard drives, faster boot times, and a graphical user interface. It also includes robust security measures such as Secure Boot to protect the boot process from malicious software.

https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface

UEFI addresses the limitations of BIOS, such as its inability to support drives larger than 2 TB or handle modern hardware efficiently. By using a modular design, UEFI supports features like networking, remote diagnostics, and firmware updates directly from its interface. The extensible architecture allows vendors to include custom drivers and utilities, making UEFI more adaptable to evolving hardware and software requirements.

https://uefi.org/specifications

A key component of UEFI is its partitioning system, the GUID Partition Table (GPT), which replaces the older MBR (Master Boot Record) format, enabling better disk management and reliability. Operating systems like Windows, Linux, and macOS fully support UEFI, offering backward compatibility with BIOS when necessary. With its advanced capabilities, UEFI has become the standard firmware interface for most modern computers.

https://www.kernel.org/doc/html/latest/efi/index.html

“When the PC starts, the firmware interface controls the booting process of the PC, and then passes control to Windows or another operating system like Linux.

UEFI is a replacement for the older BIOS firmware interface and the Extensible Firmware Interface (EFI) 1.10 specifications.

More than 140 leading technology companies participate in the Unified EFI Forum, including AMD, AMI, Apple, Dell, HP, IBM, Insyde, Intel, Lenovo, Microsoft, and Phoenix Technologies.

For more info, see UEFI specifications: http://uefi.org/specifications

Firmware that meets the UEFI 2.3.1 specifications provides the following benefits:

• Faster boot and resume times.

• Ability to use security features such as Secure Boot and factory encrypted drives that help prevent untrusted code from running before the operating system is loaded. For more information, see Secure Boot Overview and Factory Encrypted Drives.

• Ability to more easily support large hard drives (more than 2 terabytes) and drives with more than four partitions.

• Compatibility with legacy BIOS. Some UEFI-based PCs contain a Compatibility Support Module (CSM) that emulates earlier BIOS, providing more flexibility and compatibility for end users. To use the CSM, Secure Boot must be disabled.

• Support for multicast deployment, which allows PC manufacturers to broadcast a PC image that can be received by multiple PCs without overwhelming the network or image server.

• Support for UEFI firmware drivers, applications, and option ROMs.

Fair Use Source: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-8.1-and-8/hh824898(v=win.10)

• Advanced Configuration and Power Interface (ACPI)
• coreboot
• Open Firmware
• OpenBIOS
• Platform Initialization Specification
• System Management BIOS (SMBIOS)
• System Management Mode (SMM)
• Trusted Platform Module (TPM)
• Unified EFI Forum

• Unified Extensible Firmware Interface
• http://uefi.org
• https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-8.1-and-8/hh824898(v=win.10)

• https://www.intel.com/content/www/us/en/architecture-and-technology/unified-extensible-firmware-interface/efi-homepage-general-technology.html

• https://github.com/search?q=UEFI
• http://www.drdobbs.com/embedded-systems/efi-architecture/199500688
• https://web.archive.org/web/20121025093125/http://www.hardwaresecrets.com/article/UEFI-Just-How-Important-It-Really-Is/1385
• https://rodsbooks.com/bios2uefi