The Security Council’s primary responsibility is to maintain international peace and security. It is made up of 15 member states, 5 of which are permanent. These are: China, France, The Russian federation, The United Kingdom, and the United States of America. The parties are called to a meeting whenever there is “a need to settle an act of aggression or a threat to peace”. The Security Council is the only organ of the United Nations that has the power to make decisions that the member states then have to implement; it is also allowed to impose sanctions and authorize force if needed.
Link to official site: http://www.un.org/en/sc/