The 'Registry' is the system backend that is maintained by the operators of the TLD. Registrar's write new names to a central registry database, from which the authoritative root (essentially, a table of all domain names) is built. In the case of .com, .net and .org, the InterNIC runs the registry, and qualified registrars have shared access to it. In the case of many ccTLDs, the registry and registrar functions are combined within one entity.
