The skill you been looking for is call ranger stealth, and can be learn at around lvl7 if not mistake. As for armor, its literally same as its called. The higher your ranged armor rating, the lesser damage you receive from ranged attack, same goes to melee and magic. Different armor type comes with different defense rating, where some only come with high single type armor rating, and you can find some armor type which come with all 3 armor rating value, but at a lower value of course.
