The WHOIS info of a domain is a collection of a variety of details which are publicly accessed through special lookup sites or a command line. The protocol which makes this possible has the same name and you could easily see the company through which a domain name has been registered, the creation, expiration and last update dates together with the names, postal and email address of the people listed as Registrant (owner), Administrative, Technical and Billing contacts for a specific domain name. All this info has to be valid and up-to-date all the time; if not the domain address registration could be challenged. The latter is a policy of ICANN (the Internet Corporation for Assigned Names and Numbers), this means you must always make sure that the WHOIS details of your domains are legitimate. Updating the WHOIS for a number of country-code TLDs is limited, so when you register a completely new Internet domain, make sure you double-check the info you're submitting.