The number of both IGOs and NGOs has grown enormously. In 1909, scholars listed 37 IGOs and 176 NGOs. By 2000, there were 251 IGOs and 27,077 NGOs, and there are many more by now. These organizations may be regional or global. They may be specialized or deal with many issues. Also, there is considerable interaction between IGOs and NGOs, with the NGOs often affiliated with and raising new issues that are eventually dealt with by the IGOs.
There are many different kinds of IGOs. Some of the oldest are very mundane and functional. For instance, since 1874 the Universal Postal Union has allowed you to send mail to other countries. Otherwise, why should they accept mail with foreign stamps? Telephone, satellite and internet communications are facilitated by international agreements and organizations such as the International Telecommunications Union and Intelsat. Otherwise, how could you make overseas phone calls, send international emails or look up web sites in other countries? Otherwise, how can we prevent satellites from crashing into each other? There is a network of such organizations facilitating every kind of international interaction, ranging from aviation, science, commerce and transportation to professional work and social and welfare services. There are also disputes. For instance, there was controversy because other countries didn’t want the U.S. to continue to control ICANN, which governs Internet web site and domain names. ICANN wanted to maintain the same structure because it didn’t want politics interfering with their operations. They finally agreed to international participation.