Boot Loader

Resides in the MBR or in the Linux boot (/boot) directory (or partition) on the system
It's the first code to run when the MBR is accessed on the boot drive by BIOS after the P.O.S.T. process is completed
boots Linux and/or any other boot partition bootstrap-capable O/S available, so long as they are listed in the boot loader’s configuration file
can also allow users to pass various parameters to the kernel before loading the kernel.

Boot loader is typically installed during installation or by booting to a Linux partition (using a bootable device), configuring the boot loader, and installing the boot loader manually.

Linux boot loader