Survivor Traits are special abilities that distinguish particular survivors from the rest. These Traits add specific benefits in battle and are unlocked once that survivor has reached a specific level. 

Visit the survivor menu and select a character. On the right of the screen you'll find a survivor's Traits with the required level. Tap on the Trait to find out how it benefits your survivor.

Weapons and armors can also acquire specific Traits when you upgrade them. You can access equipment from the workshop. Tap on the specific item and you'll find the Traits on the right side of the pop-up.