Regional organization

A regional organization can be a collection of countries/territories for economic, political, geographical, cultural or any combination thereof. 

Geographical proximity or adjacency is the most common foundation on top of which the other factors are built though it's not necessary. To advance the interests of the grouping, typically a regional organization is formed with members comprising the constituent countries/territories through one or more bilateral or multilateral agreements.

Some examples of regional organizations are:

 ASEAN - the Association of Southeast Asian Nations 
 GCC - the Gulf Cooperation Council 
 APEC - the Asia-Pacific Economic Cooperation