Can someone provide a definition of "narcissism" as it's being used here? Is there a list of core attributes or traits that comprise it? Etiology? I've seen

Can someone provide a definition of "narcissism" as it's being used here? Is there a list of core attributes or traits that comprise it? Etiology? I've seen many discussions of this across the internet, and while there are many people who seem to know what it is, or know people who are "narcissists" or have a personality disorder, I've never seen it exhaustively described. Most comments take a form like "A narcissist will/does/does not ...", or "my narcissist dad/mom constantly ...", or "if you know a narcissist you must ...".