Narcissism is a personality trait that features an excessive preoccupation with oneself, often involving an inflated sense of self-importance, a deep need for admiration, and a lack of empathy for others. People who exhibit strong narcissistic traits may prioritize their own needs and desires over those of others, expect special treatment, and have difficulty handling criticism. 

In psychology, Narcissistic Personality Disorder (NPD) is a more extreme and clinical version of this trait. People with NPD may have an exaggerated sense of superiority, fantasize about power or success, and exploit others to achieve their goals, all while being highly sensitive to perceived slights or failures.