Whois is used to lookup records in InterNIC's main database for second-level domains.
Whois can be used as a program, or by telneting to ds.internic.net, or by contacting URL http://rs.internic.net/cgi-bin/whois
Whois performs generic, string-based searches on several databases maintained by InterNIC, the most important of these being the domain registration database. This database contains entries for all valid second-level DNS names, along with contact information and name server addresses. Another database contains thousands of contact people, arranged alphabetically. All of these records are indexed by keys, which can be used (if known) to match records exactly.