Final answer:
The United Nations was established in 1945 by 51 countries after World War II to maintain international peace and security, develop friendly relations among nations, and promote social progress and human rights.
Step-by-step explanation:
The United Nations was established in 1945 by 51 countries after World War II. Its goals include maintaining international peace and security, developing friendly relations among nations, and promoting social progress, better living standards, and human rights. The United Nations has a governmental structure led by the General Assembly and the Security Council, with the Security Council consisting of five permanent members (United States, Russia, Britain, France, and China) who have veto power.