A more thorough explanation:

The Bureau of International Organization Affairs (IO) is a department within the U.S. Department of State. Its main responsibility is to coordinate U.S. diplomatic participation in international organizations and conferences, such as the United Nations.

For example, the IO works with the U.S. delegation to the United Nations to ensure that the U.S. position is represented and communicated effectively. The IO also works with other international organizations, such as the World Health Organization and the International Atomic Energy Agency, to advance U.S. interests and promote international cooperation.

The IO plays an important role in shaping U.S. foreign policy and promoting U.S. values and interests on the global stage.