Of course self-esteem and narcissism are not the same thing. People with narcissism don't have empathy or care for others and they can ridicule others to make themselves feel better. Someone with self-esteem doesn't do that. It's kind of a paradox -- the less self-esteem one has, the more he or she has to manipulate and degrade others to feel better.
Even though narcissism and self-esteem are different, I do believe that they both have one thing in common. They both develop in childhood and have a lot to do with how our parents treated us when our personality was still developing.