Definition - What does USB Boot mean?
USB boot is the process of using a USB storage device to boot or start a computer’s operating system. It enables computer hardware to use a USB storage stick to get all essential system booting information and files rather than the standard/native hard disk or the CD drive.
All popular operating systems support the creation of a bootable USB drive that can be plugged into a USB slot to boot a computer, server or laptop.
Techopedia explains USB Boot
USB boot works much like the legacy floppy disk drive (FDD) booting capability. It is mainly used to recover, repair and install an operating system. It provides users with an alternative method to boot a system. Typically, to perform a USB boot, a bootable USB device must first be created. The bootable USB drive can be set up using a native operating system component or through various third-party utilities. The software/utility will copy all the operating system files and boot sequence into the USB drive to enable the USB boot.