Stats - Priority?

What does this do?

I believe it is the priority at which units target it (ie: the order). Think high priority = targeted first.

hm.. I think it's also the order in which they are selected, units with a higher priority would be higher in the selection thing that ones with lower priority when u select a bunch of units.

Uh...and what about Item Priorities?

I think that's for computer AI only. I think it the higher it is, the more likely the computer will pick it up before anything else around that has a lower priority.

EDIT: This must also explain computer's instant-hack-like item pick ups that they do. :/

Yes, that is. For example campaign's heroes have maximum priority to make them first in selecion groups.

Yes it is, you have 12 slots in the unit selection UI, and the priority is the order in which the units are placed.