What does uefi and legacy mean?

uefi: Unified Extensible Firmware Interface is a personal computer system specification used to define the software interface between the operating system and the system firmware as an alternative to BIOS. The Extensible Firmware Interface is responsible for power-on self-testing (POST), contacting the operating system, and providing an interface to connect the operating system to the hardware.

Legacy: In the context of computers, refers to the legacy BIOS transfer mode boot sequence: power on → BIOS initialization → BIOS self-test → boot OS → enter system. Or it refers to the English word, the basic interpretation of the legacy, bequest.

Extended Information

Introduction of uefi boot:

UEFI boot is a new type of motherboard boot entry, which is regarded as the successor of BIOS which has a history of more than 20 years, and has the advantage of increasing the speed of booting into the operating system after the computer is turned on.

UEFI compared to the traditional BIOS boot method, to put it bluntly, "skipped" the process of self-testing at startup, so the computer boot speed will be much faster, the principle of the following chart. The newest addition to the list is a new version of the UEFI system, which is now known as Legacy, which is a new mode of operation.

UEFI in addition to the ease of booting, there is one of the biggest visible features is UEFI support for graphical operation, many pro may also find that many of the BIOS is now a graphical interface, and support for the mouse operation, which is not possible in the traditional BIOS.

Reference:

Baidu encyclopedia-legacy

Reference:

Baidu encyclopedia-uefi