There are 5 barbarian camps for the guild, scattered across the world. Camps are where barbarians advance most of their skills, read notices or post their own, or buy new weapons and armour, or just hang out. At the larger camps there's more to do, such as playfighting and armwrestling. The skill can be raised directly, or by raising individual sub-skills that you might think are particularly important. Constitution is important here.
Dexterity is important here.
It also determines how much extra damage you receive when in a berserk rage. It is a simple average of all the skills contained within. This skill affects your ability to fight without weapons or to fight in brawl mode. This skills affects combat with the big sharp weapons such as axes and swords. It also affects commands such as cleave and hack that use these weapons.