When a computer is first turned on or restarted a special type of absolute loader is executed called a bootstrap loader.
A bootstrap loader is a program that resides in the computer's EPROM, ROM, or other non-volatile memory. It is automatically executed by the processor when turning on the computer.
A bootstrap is the program that initializes the operating system (OS) during startup. It referred to a bootstrap load button that was used to initiate a hardwired bootstrap program, or smaller program that executed a larger program such as the OS.
A boot loader is a type of program that loads and starts the boot time tasks and processes of an operating system or the computer system. It enables loading the operating system within the computer memory when a computer is started or booted up.