In the hands of a barbarian, this weapon deals an additional +3 damage when it’s used to score a hit against a monster that is larger than human-size. The To Hit bonus remains at +2.
In the hands of a dwarf fighter, fighter, or paladin, this is an “ordinary” +2 weapon.
When attacking creatures human-size or smaller, this is an “ordinary” +2 weapon no matter what class is wielding it.