The League of Nations was the first intergovernmental organization that was established after World War 1 in order to try and maintain peace. It was headquartered in Geneva, Switzerland and designed to be a forum for handling international disputes before they flared up into military action and caused domino effects that pulled ally nations into the conflict (as had happened with the Great War). Unfortunately, the League failed miserably in its intended goal: to prevent another world war from happening (WW2 broke out only two decades later).
The idea was for the League of Nations to prevent wars through disarmament, collective security, and negotiation. It was also involved in other issues such as drug trafficking, arms trade, and global health. Although the League disbanded during WW2, it was replaced with the United Nations, which is still going strong today.