Broadly, an international standards organization is an international organization which develops international standards.

There are many international standards organizations, but the three international organizations having the highest international recognition are the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Union (ITU). All three of these have existed for more than 50 years (founded in 1947, 1906, and 1865, respectively) and they are all based in Geneva, Switzerland. They have established tens of thousands of standards covering almost every conceivable topic. Many of these are then adopted worldwide replacing various incompatible 'homegrown' standards. Many of these standards are naturally evolved from those designed in-house within an industry, or by a particular country, whilst others have been built from scratch by groups of experts who sit on various technical committees (TCs).

ISO is composed of the National Standards Bodies (NSBs), one per member economy. The IEC is composed of “National Committees”, one per member economy. In some cases, the National Committee to the IEC of an economy may be the ISO member from that country or economy.

The World Standards Cooperation (WSC) is a cooperative effort between ISO, the IEC, and the ITU.

ISO and IEC are non-treaty international organizations. Their members may be non-governmental organizations or governmental agencies. The ITU and Codex Alimentarius are two examples of treaty-based organizations (where only governments are the primary members). The members of these organizations are the government foreign ministry, and/or appropriate regulatory body (telecoms regulator, agricultural, food safety or pharmaceuticals regulator, etc).

In addition to these organizations, there exist thousands of standards organizations that set standards within some more specialized context, such as IETF, W3C, IEEE or API. Often, these international standards organizations are not based on the principle of one member per country. Rather, membership in such international organizations is more granular having either organizational/corporate or individual technical expert members from around the globe.

source: http://en.wikipedia.org/wiki/Standards_Organizations#International_Standards_Organizations