The difference is in video outputs.
VDH - VGA, DVI and HDMI.
VD - VGA and DVI.
VH - VGA and HDMI.
Edit: the VDH version of the board also has a few extra features such as a type C USB port, an extra fan header and RGB header.
There is a couple extra features but they seem rather pointless, like a parallel port header and TPM port header.