Used for hiding certain elements of the face on certain races for certain helmets. The exact workings of this has yet to be discovered, however you can get a general idea of how this works with the information below.
Structure
Column.........Field.........Type...............Notes
1...................ID ............Integer .........Ref from ItemDisplayInfo.dbc
2...................Hair .........Integer .........0 = show, anything else = don't show? There is more to this, such each number is a different rank of facial hair to hide, or something like that? IE a value of 1020 won't hide night elf ears, but 999999 will (or -1).
3..................Beard .......Integer .........Tusks also?
4..................Earrings ...Integer .........Anything else?
5..................Unknown .Integer .........Nothing on dwarf, night elf, or gnome. Perhaps something on horde?
6..................Ears .........Integer .........