Refers to any organization with international membership or scope, such as the UN, WHO, or NGOs.
The UN is one of the most famous international organizations.
He works for an international organization.
Specifically the United Nations, while 国際機関 is a broader term for any international body.
Often a type of 国際機関, but 国際機関 can also include intergovernmental organizations.
Compound of 国際 (international) and 機関 (organization, body).