WHOIS data is the set of contact details that are assigned to a domain. The WHOIS data is the official owner of the domain. You can look up the WHOIS data for a domain with any number of online WHOIS lookup tools.
We recommend using this tool: https://whois.icann.org/en
Sometimes, malicious users or other bad actors will crawl the WHOIS database to find recently registered domains. They will obtain the e-mail addresses or phone numbers attached to domains, and then send them spam e-mails or calls. This can be combatted by hiding your WHOIS data, via our Private WHOIS.