is there an online tutorial on linux "graphics"?

[Robert P. J. Day]

  i have a couple friends who hail from the windows world who are
interested in understanding how graphics work in linux.  and by
"graphics", i mean, "ok, what is this 'X' stuff, and how does it work,
and how do you configure a graphics card, and what's all this 'AIGLX'
and so on?"

  is there, somewhere, an entry-level writeup that starts with the
basics and takes off to cover all of this up to the current advanced
stuff?  thanks.

rday