The International Organization for Standards (ISO) is a body of people headquartered in Geneva, Switzerland, that agree upon the "official" standards for all sorts of things. They are the largest such body, and by far the most impactful. Their standards have been integrated into all sorts of disciplines. ISO have 20,000+ standards that cover a huge range of topics. The "official" standard you have to pay for, but generally their content is also available freely online.
Note ISO has nothing to do with the International System of Units.
International Organization for Standardization