Trait theory analyzes personality by measuring traits and categorizing them into five factors: openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism. Openness refers to interests and willingness to try new things. Conscientiousness means being responsible versus careless. Extraversion distinguishes outgoing from withdrawn behavior. Agreeableness involves compromise versus stubbornness. Neuroticism differentiates emotional stability from nervousness.