A Boot Manager is a software program that helps a computer start up by selecting which operating system to load. When a computer is powered on, the Boot Manager presents a menu of available operating systems, allowing users to choose one if multiple systems are installed. This is especially useful for computers that run different versions of Windows, Linux, or other operating systems. The Boot Manager operates before the main operating system is loaded, ensuring that the correct system is initialized. It can also handle various boot options, such as safe mode or recovery mode, providing users with tools to troubleshoot issues. This functionality is crucial for maintaining system flexibility and user control.