There is no central body or organisation that governs the Internet. The Internet is described in many RFC documents - documents wrote by the designer of the Internet's architecture - as a system of "autonomous networks who voluntarily interconnect". Autonomous is the critical word - in relation to central Internet governance - as it's meaning in relation to nations / regions is "having the freedom to govern itself or control its own affairs." Therefore, it should be clear that the Internet is a system of computer networks, who govern themselves, and voluntarily interconnect using the same Internet software (Internet Protocol Suite). The only aspect of the Internet that does need management - some may refer to it as governance - is the number and name management of the Internet Protocol Suite and the design of the Internet Protocol Suite.
Number and name governance: when computer networks interconnect using the Internet Protocol Suite they are assigned an IP address - so that data packets can be formatted with source and destination network addresses. Internet applications, such as Skype, need to use a specific port number so that transport layer protocols (TCP and UDP) can establish host-to-host connectivity. Host names (human alphanumeric readable nicknames) are used by the the Domain Name System (DNS) to easily locate an Internet resource. All of these number and name resources of the Internet need to be managed. The Internet was primarily developed and funded by the federal government of the United States - therefore, the U.S. government always had ultimate authority upon the organisations that managed the number and name resources of the Internet (IANA). More recently, it was the U.S. Department of Commerce that provided oversight for ICANN and IANA: these organisations currently manage the assignment of IP blocks to global regions and the Domain Name System (DNS). On the 1st of October, the U.S. Department of Commerce freed ICANN from it's contract of oversight: the Internet's namespace management is now an international multi-stakeholder arrangement.
Internet Protocol Suite governance: The Internet Society (ISOC) provides overall leadership for designing the Internet Protocol Suite and overall leadership for setting education policy and access initiatives. The Internet Society (ISOC) is funded through donations and membership fees; tech firms like Sun Microsystems, Inc. have been referred to as a major "Donor" to the Internet Society (ISOC) in RFC 2339. RFC 3271, titled "The Internet is for Everyone" outlines the philosophy of the Internet Society (ISOC). Historically, the design of the Internet Protocol Suite (TCP/IP) was overseen by the U.S. Department of Defense (DARPA) in the 1970's and 1980's. However, by the early 1990's, the Internet's backbone networks were changing from federally funded networks (NSFNET) to large commercial networks who would sell access to the general public. The Internet Society (ISOC) was founded in 1992 to replace the U.S. Department of Defense role in funding and providing leadership in the design of the Internet Protocol Suite (TCP/IP) and setting overall policy.
Therefore, while ICANN and the Internet Society (ISOC) dictate how the technical architecture of the Internet is designed and operates, they have no authority to enforce policy upon the autonomous computer networks that use it. National governments, where autonomous computer networks are located, do however, have authority upon their behaviour: many authoritarian national governments have set in place censorship systems so that users of these networks cannot access specific resources on the Internet. Internet governance has been discussed - debated without coming to any clear consensus - by a United Nations (UN) organisation: Working Group on Internet Governance (WGIG). This led to the creation of the Internet Governance Forum (IGF); however, neither of these organisations has so far managed to assert any authority upon ICANN or ISOC. WGIG defined Internet governance as: "Internet governance is the development and application by governments, the private sector and civil society, in their respective roles, of shared principles, norms, rules, decision-making procedures, and programmes that shape the evolution and use of the Internet."