There's a zillion degrees of narcissism! Well, maybe I exaggerate.
Everyone has narcissism, that is what makes us love ourselves, or like ourselves.....that is often called healthy narcissism - it's in balance. You love yourself, so that others can love you, your self-esteem is high, you are self-confident, you don't need to bring others down to make yourself feel better, you are emotionally self-sufficient.
But, in some people it's not so balanced, their self-love scale is set at 'too high', and that has many varying degrees of scale too.
People with strong narcissistic traits would be described as being arrogant, selfish, self-absorbed, uncaring and would display little empathy for other's situations. The stronger the traits, the more selfish and arrogant the person. The term narcissistic personality disordered would describe someone with a lot of unhealthy narcissistic tendencies and traits, and who has never learned from life lessons, has never developed empathy, are self-sabotaging of their life, careers and relationships, are predatory in nature, are emotional sponges (where they constantly drain others around them without giving back) and generally 'crappy' people to know, and they would have a history of the same behaviours. Some NPD's go as far as fitting the psychopath characteristics too.
So that is some examples of how diverse narcissism is.