Registry, Registrar and Registrant. What do these words mean?

A registry is a company or organization that maintains a centralized registry database for the Top-Level Domains. Currently there is only one Registry for every Top-Level domain, .com, .net and .org. NSI Registry maintains this Registry.
A registrar is an ICANN accredited company or organization that is authorized to provide registration services for the top-level domains such as .com, .org and .net. Registrars have contractual agreements with their customers. A Registrar submits all newly registered domains into the Registry.
The Registrant is the owner of a Domain Name. The owner may be an individual or an organization to whom a specific Domain Name is registered. When a Registrant registers a Domain Name and enters a contractual agreement with the Registrar, they are the legal owner of a domain name for a specific period of time. The Registrant is bound by the terms of the service agreement. For example, Toni Smith (Registrant) registers the name '' through the Registrar who in turn writes the name to the central database (NSI Registry).
Formed in October 1998, the Internet Corporation for Assigned Names and Numbers is a non-profit, private sector corporation with a volunteer board of directors. ICANN was formed with the chief responsibility for coordinating four key functions for the Internet: the management of the Domain Name system, the allocation of IP address space, the assignment of protocol parameters, and the management of the root server system. For a company or organization to operate as a Registrar, they must first obtain ICANN accreditation. To view the ICANN website click here.
A registry provides direct services to registrars only, not Internet end-users. The Registry database contains only Domain Name service (DNS) information (Domain Name, name server names and name server Internet Protocol [IP] numbers) along with the name of the Registrar that registered the name and basic transaction data. It does not contain any Domain Name Registrant or contact information.