What is ICANN?
ICANN is short of Internet Corporation for Assigned Names and Numbers. It is a non-profit organization that manages and maintains different databases related to namespaces and number spaces on the Internet.
In really short: ICANN coordinates the use of domain names and IP addresses so that the Internet, as we know it, can function without conflicts. Thanks to it, you can’t have two people who have the same domain name or two computers with the same IP address.