Stands for "Internet Corporation For Assigned Names and Numbers." The ICANN is an non-profit corporation that is responsible for allocating IP addresses and managing the domain name system.
Every computer connected to the Internet, from servers to home PCs, has an IP address. However, it would be unrealistic for the ICANN to directly assign each computer an individual IP address. Instead, the ICANN allocates blocks of IP addresses to companies, educational institutions, and Internet service providers. These organizations then allocate IP addresses to computers that use their Internet connections.
While the ICANN is a US-based organization, it is also a global Internet community. According to ICANN's website, the organization is "dedicated to preserving the operational stability of the Internet; to promoting competition; to achieving broad representation of global Internet communities; and to developing policy appropriate to its mission through bottom-up, consensus-based processes" (icann.org).