ICANN (Internet Corporation for Assigned Names and Numbers) is the international corporation that has final control over managing domain names. You will never deal with them directly.  You may see little notes on websites that say “ICANN Certified.”  All that means is that that site claims to be registered and contact directly or indirectly with ICANN at some point in its business operation.  To the average user, all issues related with ICANN should be handled by someone else, so you shouldn’t worry about them at all.