Bootloader

Briefly, a bootloader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the operating system kernel software (such as the Hurd or the Linux). The kernel, in turn, initializes the rest of the operating system (e.g. GNU).

some example bootloaders are:

X86:
 * Lilo
 * Grub
 * Syslinux
 * U-Boot

ARM:
 * APEX
 * Blob
 * U-Boot

MIPS:
 * U-Boot

PowerPC:
 * U-Boot

Bootloader_Security_Resources