Drum Map Settings - Head Symbols & Voice ??

I’m using Cubase 5 with a drumset all triggered with a DDrum 4SE brain. We have gotten it working ok but I now notice lots of little details that I have no clue about and can’t seem to find anywhere easily on the net… Here goes:

What do the “head symbols” do? and what are their differences?

What does the “voice” setting do?