What is a registry?
A Registry (or Registry Operator) is the company that maintains a database of all domain names registered under a given top-level domain (TLD) such as .com, .design, .dentist, etc. Some registries include Donuts, Famous Four Media, and Top Level Design, the parent company of Porkbun.
Registries differ from registrars (such as Porkbun, GoDaddy, Enom, etc.) in that they do not sell domain names directly to the public. Instead, they are responsible for maintaining the infrastructure of the registry database, overseeing wholesale pricing, ICANN compliance, and various issues related to trademark protection. Registries are also required to run special DNS servers to host certain records such as "glue" records and the NS records that designate the authoritative nameservers for a domain.