A boot loader is a small program that runs when a computer or device is powered on. Its main job is to load the operating system into memory so that the device can start functioning. Boot loaders are essential for initializing hardware and preparing the system for use. They often provide options for selecting different operating systems or recovery modes. There are various types of boot loaders, such as the GRUB for Linux systems and the Windows Boot Manager for Windows. Each boot loader has specific features and configurations, allowing users to customize their boot process according to their needs.