Would you please tell me everything you know about narcissism and narcissistic personality disorder?

I have read tons of webpages recently, so I have a pretty good idea.. but I feel like I can not get enough information to satisfy my desire to really understand it.
I know there is a difference between healthy narcissism and toxic narcissism… I want to learn more about those with excessive self-love.
Are there varying degrees of narcissism?
Are all narcissists exploitative, and if so, are they exploitative of everyone around them… or do they only surround themselves with people they can exploit?
Are all narcissists pathological liars?
What are the differences between psychopathy and narcissism?