According to the United Nation's website "The General Assembly (GA) is the main deliberative, policymaking and representative organ of the UN. Decisions on important questions, such as those on peace and security, admission of new members and budgetary matters, require a two-thirds majority. Decisions on other questions are by simple majority.
The Security Council has primary responsibility under the Charter of the United Nations for the maintenance of international peace and security. Chapters V-VII, Articles 23-54, of the UN Charter concern the Security Council.
According to the U.N.'s website, the Economic and Social Council (ECOSOC) is the principal body for coordination, policy review, policy dialogue, and recommendations on economic, social and environmental issues, as well as for the implementation of the internationally agreed development goals." In addition, it also coordinates the work of specialized agencies.
The International Court of Justice (ICJ), the main judicial body of the United Nations, was established in 1945 as a product of the drafting of the Charter of the United Nations. The Court’s constitutive statute was subsequently annexed to the Charter. All members of the U.N. are ipso facto parties to the statute of the Court ( See Art. 93(1), UN Charter). A state which is not a member of the U.N. may become a party to the Statute of the ICJ on conditions determined by the General Assembly upon the recommendation of the Security Council. (See Art . 93(2), UN Charter).