The whois data of a domain name provides a lot of useful information.
This includes contact information of the person who owns and administrates the domain, when the domain name expires, the domain name servers, and what IP address or hosting company the domain is currently pointing to.
Many whois tools offer additional information for a fee. For example, they can provide a record of all past whois information for that domain.
This kind of information is very useful if you are trying to get in touch with the owner of a domain you want to purchase or if you want to check the history of a domain name.
Be aware, however, that many domain name owners pay for a feature known as Domain Name Privacy that hides all of their personal information; and despite not being allowed to do so, many people also enter false information when they register a domain. This can make finding the owner of a domain much more difficult.
This page lists a selection of whois lookup tools that will help you see the whois information of a specified domain.
DomainTools is a large resource that provides many useful domain name checking and monitoring tools. Their whois lookup tool provides a wealth of information including registrant information, past whois records, hosting info, and more.
ICANN is the non-profit organisation that manages the domain name system.
Their whois lookup tool provides essential information about the domain name, where the domain is registered, the domain creation date, and the name servers that the domain is pointing towards.
Nominent is the .uk domain name registry which overseas top-level domains such as .co.uk, .uk, org.uk., and .me.uk. You can use their whois lookup tool to check the whois information of any UK domain name.
Whois Search is a simple whois lookup tool that I have used frequently over the years. It will display whois information of any domain you enter. Nothing more. Nothing less.