The WHOIS info of a domain name is a collection of a variety of details that are publicly accessed through special lookup websites or a command line. The protocol which makes this possible carries the same name and you could easily see the firm through which an Internet domain has been registered, the creation, expiration and last update dates along with the names, postal and e-mail address of the people listed as Registrant (owner), Administrative, Technical and Billing contacts for a particular domain. This info has to be correct and up-to-date at all times; if it's not the domain address registration may be challenged. The latter is a policy of ICANN (the Internet Corporation for Assigned Names and Numbers), therefore you should always ensure that the WHOIS details of your domains are valid. Updating the WHOIS for a variety of country-code TLDs is limited, so any time you register a brand new domain name, make sure you double-check the info that you are submitting.