What is moral nihilism?

A nihilist is someone who would accept Nihilism, which is the concept that everything is nothing, to put it in a single sentence. We are of no real substance, and all we have is essentially nothing. Where most people believe our actions will bring a different reality, a nihilist would see any action as irrelevant since nothing we do matters.

This is my view on it from reading Nietzsche, discussing some Kierkegaard, and a light base of my own thinking on the potential uselessness of reality.