Whois

Whois is an Internet service that finds information about a domain name or IP address. If you enter a domain name in a WHOIS search engine, it will scour a huge database of domains and return information about the one you entered.

This information typically contains the name, address, and phone number of the administrative, billing, and technical contacts of the domain name. WHOIS can also be used to simply check if a certain domain name is available or if it has already been registered.

To see the WHOIS service in action, check out www.whois.com