Have you used WhoIs Look-Up?
With a store or a person there is usually a physical address to which you can go. On the web the addresses are virtual. A website can be housed on any Internet connected server anywhere in the world. WhoIs information is maintained to connect the virtual address with the party responsible for that virtual address.
The WhoIs System
If you need to find somebody in the real world you may look in the phone book. If you need to see them you may find the address and visit them. In the virtual world the owner of a website may be in one country and the site on a server half way around the world.
The WhoIs system keeps the records of who is responsible for a website (domain name). There is information about the registered owner of the domain name, the registrar that is responsible and when the registration expires.
WhoIs look-up is a service that is authorized to access the WhoIs database and provide the information to inquiring parties. This is usually provided as a free service.
There are private registrations available from the registrars, usually for a small additional fee. With a private registration the whois look-up will not list the name of the registrant, but will provide a means to contact the site owner.
There are three major whois databases maintained for various parts of the world. A public whois look-up service will interrogate all of the whois databases until it finds the whois information. Each of the databases has their own look-up engine and is available for use.
In addition to finding the registration information for a domain name many whois tools will find information on an IP address. Each computer that is connected to the Internet has an IP address, be it a server housing a website or your personal computer in your home.
IP lookup will not provide someone your home address because it does not have the resolution, but usually it will tell you the ISP or body that is responsible for the block of IP addresses of which yours is one.
There is a good bit of information available about properties on the Internet. The tool you use to find that information is WhoIs Look-up. Just do a search for whois and you will find many places where the service is offered.