Ranger Skill Woodcraft

In patch 0.8.8 you guys wrote on the patch notes:
"*New skill Woodcraft added to the Ranger class."

I have a ranger now and i'm scratching my head is it's worth putting more points into it, because i don't know what are those +1+2+3 enhancements that the tooltip says... is it armor, is it damage, is it random stats, is it random spell buffs?

and is it only for the hero or for the army too?
It would be great to work like tactician or tactician to work like that "temporary buff all units when hero casts"