[CentOS] Don't understand how to re-partition this setup or why it was made like this

Hello,

I did df -h on my CentOS 6.4 machine.

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_ysg-lv_root
                       47G  8.8G   36G  20% /
tmpfs                 948M  372K  947M   1% /dev/shm
/dev/sda1             485M   62M  398M  14% /boot
/dev/mapper/vg_ysg-lv_home
                      4.6G  2.7G  1.7G  63% /home

What I don't understand is why is /home so tiny and how can I re-partition
this without having to nuke and rebuild my machine?