Slightly Confused About Leopard Install Options

Ok so I've been searching through the forums and trying to figure out what the difference between Upgrade and Archive and Install are. As I understand it, Upgrade does just that: upgrades your computer to Leopard while leaving all your files in place. Now, does Archive and Install do the same thing as upgrade, but make an extra copy of your files in case something goes wrong... or does it create a separate folder with your files, installs Leopard, and then forces you to fix all your files again (as in, would my songs still be in iTunes with all my playlists and play counts, or would I have to put them back into the program?).

If you could help me clear up this confusion, it would be greatly appreciated. Thanks!

 

^ I read that article earlier but I was still slightly confused. If it says my Home folder will be preserved, then that means all my music and photos will already be in iTunes and iPhoto as they were before the install, right?

And also, if it doesn't save my 3rd party apps, what's the best way to keep those intact?

 

So let me get this. Archive and Install basically does the exact same thing as upgrade, but makes Tiger into it's own folder, that you can delete at a later time?