Narcissism is a personality disorder characterized by an excessive sense of self-importance and an inflated sense of self-worth. People with this disorder often have an exaggerated need for attention and admiration, and may have little empathy for others. Narcissistic personality disorder is a type of Cluster B personality disorder, which are characterized by dramatic, emotional or erratic behaviors. Narcissism is a spectrum, and Narcissistic Personality Disorder is the severe end of the spectrum.
For example, a narcissistic person may constantly talk about their own accomplishments and talents, and may become angry or resentful if they are not given the admiration they feel they deserve. They may also have a lack of empathy towards others and be unwilling to understand or acknowledge the feelings and needs of those around them.