The WHOIS info of a domain is a collection of many details that are openly accessed through special lookup sites or a command line. The protocol which makes this possible has the same name and you could very easily see the company through which a domain address has been registered, the creation, expiration and last update dates in addition to the names, postal and email address of the individuals listed as Registrant (owner), Administrative, Technical and Billing contacts for a particular domain address. All of this info must be valid and up-to-date constantly; if it's not the domain name registration may be challenged. The latter is a policy of ICANN (the Internet Corporation for Assigned Names and Numbers), so you must always make certain that the WHOIS details of your domains are valid. Updating the WHOIS for several country-code TLDs is limited, so whenever you register a completely new domain name, you ought to double-check the info that you are submitting.