[CentOS] Reading the Output of DF

I am not sure how to interpret  the output of the DF -h command.

Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      112G   12G   95G  11% /
/dev/hda1              99M   12M   82M  13% /boot
none                  125M     0  125M   0% /dev/shm

 The filesystem Centos is using is new to me since I have RH 9 on my 
other server.  I assume the FS combines my two drives into the virtual 
drive.

What I do not understand is the "none" filesystem and how that relates 
to the "VolGroup00-LogVol00", if at all.

Todd

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