Question

what do you mean by boot

Answer 1

The term boot is used to describe the process taken by the computer when turned on that loads the operating system and prepares the system for use.

Answer 2

boot (as a verb; also "to boot up") a computer is to load an operating system into the computer's main memory or random access memory (RAM). Once the operating system is loaded (and, for example, on a PC, you see the initial Windows or Mac desktop screen), it's ready for users to run applications.