The Threat From the Deep
Traits and Flaws
Traits are aspects of a character’s personality, background, or physique that make him better at some activities and worse at others. In many ways, traits resemble feats: A character can have only a limited number of traits, and each trait provides some benefit. Unlike feats, however, traits always carry a corresponding drawback. In addition to their game effects, traits suggest characteristics about the character’s personality that might lead to interesting roleplaying opportunities. Together with a character’s class and feat selection, traits offer a way for game mechanics to encourage deeper character backgrounds and consistent roleplaying.
Flaws are like the flip side of feats. Whereas a feat enables a character to be better than normal at performing a task (or even to do something that normal characters can’t), a flaw restricts a character’s capabilities or imposes a penalty of some sort. A player may select one flaw when creating a character. After 1st level, a character cannot take on additional flaws unless the DM specifically allows it. Each flaw a player selects entitles his character to a bonus feat.
A greater explanation and a list of traits and flaws can be found on the d20srd