Domain name registries are organisations that manage and catalogue all information relating to top-level domains (TLDs), i.e. the text strings that categorise an Internet domain.
The main activity of the registries consists in creating one or more databases containing all the data associated with a domain name, such as the entity responsible for its sale (called registrar) or information about its buyer (registrant). The registries also assign a specific ID to each domain name they manage.
There are various types of registry, all accredited and controlled by ICANN, depending on the TLD. Some registries, however, manage multiple categories of TLDs.
In addition to constantly updating TLD information, registries help manage the registration process by providing the list of available domain names to registrars. This process is made possible by the close collaboration between the registry and WHOIS, a system that manages all Internet domain information.