A domain registry is the organization that manages the master database of all domain name registrations for a TLD such as .com, .org, or .uk. The registry maintains the authoritative records of who owns each domain, the nameservers pointing to that domain, and other technical details that make domain resolution possible.
Registries are distinct from domain registrars. A registrar is the retail service you buy a domain from; the registry is the backend authority that actually records the registration. When you purchase a domain through a registrar, that registrar submits your registration details to the appropriate registry, which stores and publishes them. For example, VeriSign operates the .com registry, while thousands of registrars (like GoDaddy, Namecheap, or others) sell .com domains on your behalf.
Each registry publishes a WHOIS database containing publicly searchable registration data, including registrant details, nameserver information, and SOA records. When someone looks up a domain's nameservers, they're querying the registry's records.
Registries also enforce rules for their TLDs—such as eligibility requirements, renewal periods, and EPP codes (auth codes) needed to transfer domains between registrars. They maintain the technical zone files and ensure the DNS infrastructure works reliably for all domains under that TLD.
NoteA registry is not the same as a registrar. The registry is the authoritative keeper of domain records; a registrar is the service through which you register and manage your domains.