Guide on Unified Extensible Firmware Interface (UEFI)

What is UEFI:
The Unified Extensible Firmware Interface (UEFI) is a specification for software program which is responsible for linking a computer's firmware to its operating system. It is the successor to the Basic Input/Output System (BIOS)

Why it's Important:
UEFI ensures system and hardware integrity throughout the boot process, supports booting from large disks (>2.2TB), provides better boot times and administrative capabilities, and it is capable of remote troubleshooting and repair.

How UEFI Works:
When the computer is turned on, the UEFI firmware loads the installed operating system and all necessary hardware components. It also provides a wide range of options for booting both locally and remotely, and the ability to use BIOS-based devices.

Answering Questions on UEFI in an Exam:
To answer questions regarding UEFI, understand its main functions, strengths and improvements over BIOS. Know that the UEFI initializes the system and hardware, launches the bootloader, and determines boot configurations. Acknowledge its importance in system security and large disk support.

Exam Tips: Be sure to explain that UEFI provides a more flexible and programmable interface, focus on its capability of faster boot times, secure boot feature and support for larger disks. Remember the difference between UEFI and BIOS and mention how the UEFI removes many of the limitations of the traditional BIOS.

NOTE: The detailed workings of UEFI might be an overkill for starter level exams like CompTIA-A+.