What is domain name WHOIS lookup?
A domain name can be registered with a domain name provider. For every application of a domain, the name is registered in the system of the domain name registrar. The registrar features a database with all registered domain names and keeps records of all the owners' names and other business details per domain name.
All information pertaining to the domain name and domain name holder is readily available to the public. Retrieval of, or a request for, this information is called a "WHOIS" lookup, a contraction of the words "who is".
A whois lookup is most often used to verify the owner of a domain name or to gain contact with the domain name owner. In some cases, the whois server is also used to collect email addresses of domain name owners in order to send them email spam. There are however more and more restrictions regarding the large-scale consulting of public whois databases, mainly to counteract spam messaging.