What is ICANN?
ICANN is the International Corporation of Assigned Names and Numbers. ICANN is the nonprofit organization responsible for coordinating the maintenance, policies and procedures of several databases related to the namespaces of the Internet as well as ensuring the network stability and security.
What is a registrar?
ICANN accredits companies which sell domain names and are held to a number of standards outlined in in their Registrar Accreditation Agreement. Registrars also sign contracts with Registrar Operators so they may sell their TLDs.