Barbarian traits
Traits are passive skills. Points spent in these grant bonuses that affect other aspects of the character. Traits are not displayed in the skill listing, but are on their own separate Traits menu.
Unlike skill points, which are earned at every level up, Trait points are only awarded every other level. Only on odd numbered levels: 1, 3, 5, 7, and so on, up to 59.
Known Barbarian Traits
This listing comes from the Blizzcon 2010. It should be considered preliminary and subject to change and revision. In fact, the D3 Team said at Blizzcon that traits were very new and still undergoing development, and that with over 30 Traits for the established characters, there were probably too many of them at this point for players to make informed choices.
Traits become available in bunches, usually every 4 levels.
References