The United Nations (UN) is an intergovernmental organization. Hence, the members are sovereign states from all over the world. On June 26th, 1945, members of 51 sovereign states signed the UN Charter. It came into force on October 24th, 1945. So, officially founding the United Nations.
The Charter (found here) is the founding document. It describes the motives and missions of the organization. The need for such an organization came with World War II. and the failed Versailles system and League of Nations. Hence, the first and foremost goal of the UN is to protect peace and security. Besides, the UN is here to protect human rights, fairness, and justice. The principal is freedom and friendly relations among all nations.
By joining the UN, every state must commit to common goals. Every state is sovereign and equal to one another. They shall prevent the use of force and better settle conflicts by peaceful means.
Organs of the United Nations
New York City is the home of the HQ of the UN. However, it has many more offices, including the second largest one in Geneva, Switzerland. Besides, it has many subsidiaries such as WHO, ICAO, WTO, or UNESCO.
Moreover, the UN itself has multiple organs. The Charter defines their field of work and their rights. The most important is the General Assembly. It meets once a year to adopt the budget, accepts new members, and creates resolutions based on various reports. Each member country has a representative. It also has six supportive committees. Hence, it has 193 members (2021).
The UN Security Council is responsible for world peace. Thus, it tries to resolve conflicts. It has 15 members, five permanent with a veto right, and ten changing members.
Significant is the International Court of Justice. The goal of the “World Court” is to settle conflicts between nations according to international law. The court is located in the Peace Palace in Hague.
The Secretariat manages the organization. The leader of the Secretariat is the Secretary-General. That is the highest-ranking official. At last, the UN has an Economic and Social Council and UN Trusteeship Council.