LILO is the Linux boot loader. It includes combined boot sector,
generic chain loader, map installer, and a simple boot partition setter.
LILO allows booting from multiple disks, and can have menus for choosing
different boot images. LILO is also able to pass command-line options
to the Linux kernel.

LILO does not depend on a specific file system, can boot Linux kernel
images from floppy disks and from hard disks, and can even act as a
"boot manager" for other operating systems.

LILO should be ran whenever any part of the system that it knows about
changes, e.g. after installing a new kernel.