The WHOIS info of an domain is a collection of various details which are freely accessed via special lookup websites or a command line. The protocol that makes this possible carries the same name and you can easily see the organization through which a domain name has been registered, the creation, expiration and last update dates in addition to the names, postal and email address of those listed as Registrant (owner), Administrative, Technical and Billing contacts for a specific domain. This information must be correct and up-to-date at all times; if it's not the domain name registration can be challenged. The latter is a policy of ICANN (the Internet Corporation for Assigned Names and Numbers), so you should always make certain that the WHOIS details of your domain addresses are valid. Updating the WHOIS for a number of country-code TLDs is limited, so any time you register a completely new domain address, you ought to double-check the information that you are submitting.