The WHOIS info of a domain is a collection of a number of details that are freely accessed using specific lookup websites or a command line. The protocol that makes this possible bears the same name and you could very easily see the company where a domain name has been registered, the creation, expiration and last update dates in addition to the names, postal and e-mail address of the individuals listed as Registrant (owner), Administrative, Technical and Billing contacts for a particular domain name. All of this info must 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), so you must always make sure that the WHOIS details of your domains are accurate. Updating the WHOIS for several country-code TLDs is limited, so whenever you register a new domain name, you ought to double-check the information that you're submitting.