WHOIS data is a publicly available information database that contains details about registered domain names and their respective owners or registrants. It provides information such as the domain name's creation date, expiration date, registrar, and contact details of the registrant, including their name, address, email address, and phone number.

When a domain name is registered, the registrar collects this information from the registrant and maintains it in a WHOIS database. This data is often used for administrative and legal purposes, including identifying the domain name owner, verifying domain ownership, and resolving any disputes or issues related to the domain.

However, it's important to note that with the introduction of privacy protection services, some registrars offer the option to mask the registrant's personal information in the WHOIS database. This is done to protect the privacy and security of domain owners, preventing their contact details from being publicly accessible.