A bootloader is a small program that runs when a computer or device is powered on. Its main job is to load the operating system, such as Windows or Linux, into memory so that the device can start functioning. Bootloaders are essential for initializing hardware and preparing the system for use. There are different types of bootloaders, including GRUB for Linux systems and UEFI for modern computers. They can also provide options for selecting different operating systems or recovery modes. Overall, bootloaders play a crucial role in the startup process of any computing device.