Registrar: A registrar (or "Domain Name Registrar") is an organization like
OpenSRS or Network Solutions that has control over the granting of domains
within certain TLDs (Top Level Domains, like the generic .com, .org, and .net).
Registry: The registry is the backend that registrars have shared access to. Each
registrar writes new names to a central registry database, from which the
authoritative root (essentially, a table of all domain names on the Internet) is built.
Registrant: A registrant is the person or company who purchases a domain name.