1) Oligarchy is a small group of extremely powerful people controlling the financial health of the nation or a form of government in which all power is in the hands of a few persons. It is government by a small group exercising control especially for corrupt and selfish purposes using bribery, if you do this for us we will give you this; intimidation, do this for us or we will do this to you; and coercion, we have the full force of the police and the army. This is government by a few for a few.
2) Democracy is a large group of investors/citizens controlling the financial health of the nation by controlling the political parties through free elections and ethical conduct boards. This is government controlled by judicial procedure whose members are accountable to the courts for any laws broken. This is government by the people for the people.