It's not something you really play with for the sake of it - it's an underlying system tool.

Before it was in all the installers, I played with it a little and wrote up some notes on the wiki at http://www.wlug.org.nz/LVMNotes (specifically about how to do it on one drive).

Nowadays, as Ian says, you just tell the installer to do it, and it does.  It's similar to the volume management in Windows and other Unix-like OSes.

Plus, it also lets you do cool things like this: http://www.wlug.org.nz/SambaShadowCopyHowto

Craig