Taken from
http://www.ccm.ece.vt.edu/~lscharf/samd/?topic=Linux&title=Lilo :

Lilo
Keywords: intel pc boot process /sbin/lilo /etc/lilo
Date Created: 2002-03-30
Author: Luke Scharf <luke@vt.edu>

Knowing how the PC boots is very helpful in troubleshooting the issues
that come up on multi-boot PCs and cantankerous tools like LILO.

Be warned, though, that you have to be comfortable thinking about the PC
without the nice abstractions provided by the operating system. Whenever
someone says "I want to put Linux on my D drive," I know it's going to
be a long day.

If you're interested in learning about the PC boot process, here are
some good references:

    * The BIOS boot process:
      http://www.execpc.com/~geezer/osd/boot/index.htm#bios
    * LILO Technical overview:
      http://metalab.unc.edu/pub/Linux/system/boot/lilo/lilo-t-21.ps.gz
    * The LILO executable man page:
      http://www.die.net/doc/linux/man/man8/lilo.8.html
    * The /etc/lilo.conf man page:
      http://www.die.net/doc/linux/man/man5/lilo.conf.5.html

Some major distributions (RedHat) are phasing out LILO in favor of grub.
Making grub work requires much less background-knowledge than LILO and
should remove another obstacle between Linux and The Average User.