The domain names industry is based on what is called the Triple-R or RRR Model: Registry – Registrar – Registrant.
The Registry manages and administers one or multiple Top-Level Domains. For example, Verisign is in charge of the .com TLD.
The Registrar delivers domain names License Agreements to clients. Unlike Registries, Registrars manage multiple TLDs and offer additional services most of the time. Registrars are accredited companies. For example, Netim is a Registrar.
The Registrant is the owner of a domain name: you!