Having a solid grasp on BIOS helps understand UEFI better. Let us begin with a brief look at how a BIOS functions, and then move into UEFI. Feel free to jump ahead if you already know how BIOS works.
BIOS is responsible for your computer being able to boot and BIOS stands for basic input output system.
In layman terms, BIOS performs the following functions-
The BIOS setup lacked the ability to load any more than that first 512 MB block. Hence a multi-stage process to get things up and running was needed. This is where UEFI came in and solved the problem.
UEFI can act as an interface between a traditional BIOS and the operating system. Like BIOS, it presents a standardized view of the hardware to the operating system, allowing operating system makers to build on top of it and have their Operating Systems work on a variety of motherboards.
Parallelly, UEFI plays the role of an abstraction layer between the firmware that acts as a BIOS and the operating system. Creators are at liberty to build UEFI implementations that are complete top-to-bottom and do not need any firmware below them in the stack.
All Modern operating systems are compatible with UEFI. The UEFI standard is favoured with the support within the industry already. Companies like Intel, AMD, Apple, Microsoft, and a number of BIOS and motherboard makers are aboard The UEFI standards organization. As a result, UEFI is not just some dead standard left in the industry's wake like so many other initiatives but will be the way forward.