BlizzCon 2010: Diablo III “Traits” Explained
Traits are basically class-specific “passive skills.” They are “passive” in the sense that they do not award actual combat abilities, but instead augment existing core attributes. They do things like increase armor, resistances, proficiencies in certain spell types, etc.
Traits have an entirely separate management screen from skills, and they have very cool, class-specific titles like Inner Rage for the Barbarian (increases power), and Prismatic Cloak for the Wizard (increases armor).
Each class has 30 traits, and you can spend 1-5 points on each trait (which further increases its effectiveness). The catch is you only spend points on traits every other level, so choose wisely.
Further combating the fact that “passive skills” can sound boring, Wilson explained that they’re making a big effort to “make numbers cool.” To do this, each trait upgrade will feature a significant increase in statistics. Don’t expect to spend a whole trait point for “+.5 increase in armor.” The numbers will be 50%, 100%, big fun numbers.