What exactly is Nihilism?

It doesn`t mean that values and morals are fake, it just means that they are destitute of objective value. According to most nihilistic philosophies, the world, objectively, has no meaning and no purpose. Things happen randomly, without a purpose behind them - they just happen. People are the ones who, subjectively, create a meaning and a sense to what happens. So, values and morals exist in our minds, not in the natural world. The ability of creating sophisticated meanings and explanations are what distinguishes humans from animals. Animals don`t have values or morals, they act by instinct. The fact that we have values and moral, and (try) to live by them is what makes us humans, and what allows us to live in complex societies.