Whois is a publicly available database for domain names that lists the contact information and the name servers that are associated with a domain name. Anyone can access the Whois database by using the WHOIS command, which is widely available. It's included in many operating systems, and it's also available as a web application on many websites. The Internet Corporation for Assigned Names and Numbers (ICANN) requires that all domain names have publicly available contact information in case someone needs to get in contact with the domain name holder.