The United Nations was created after World War II to provide an international forum that would develop positive relationships between countries, promote peace and security around the world, and establish international cooperation in solving international economic, social, cultural, and humanitarian problems. See the Preamble of the United Nations Charter, which outlines the goals of the U.N.
The major organizations of the U.N. are the Secretariat, the Security Council, and the General Assembly.
The Secretariat is the administrative center of UN operations, and is headed by the Secretary-General, who is the director of the United Nations.
The Security Council is responsible for establishing and maintaining international peace. Its main purpose is to prevent war by settling disputes between nations. The Security Council has 15 members. There are five permanent members: the United States, the Russian Federation, Britain, France, and China; and 10 temporary members who serve two-year terms.
The General Assembly is the world's forum for discussing matters affecting world peace and security, and for making recommendations concerning them. It has no power of its own to enforce decisions. It is composed of the 51 original member nations and those admitted since, a total of 192.