What is a domain name?

A domain name is a word or phrase entered into the address bar of an Internet navigator to access a specific website. Simply put, a domain name is an online identity for the owner of a website.

Domain names help translate IP addresses into words. A domain name is a name that identifies one or more IP addresses; for example, the domain name microsoft.com represents about a dozen IP addresses.

The Internet is IP address based, not domain name based, so every web server needs a Domain Name System (DNS) server to translate domain names into IP addresses. The DNS stores and associates many types of information with domain names and helps translate domain names into IP addresses.

Internet users use domain names as URLs, i.e., uniform (or universal) resource locators? Domain names are used in URLs to identify specific web pages. Take the URL http://www.pcworld.com/index.html, in which the domain name is pcworld.com.

Each domain name has a suffix, which is called a top-level domain (TLD). A TLD indicates the category to which a domain name belongs. There are a limited number of TLDs, such as .gov (government agencies), .edu (educational institutions), .org (organizations), .mil (military), .com (commercial businesses), .net (web organizations), .ca (Canada), .uk (United Kingdom), .de (Germany or German), .us (United States), and so on.

Technically speaking, domain names are host names. Many times, domain names are referred to as "network addresses", which is technically incorrect. Domain names and host names are often used interchangeably, but there are subtle technical differences between the two.

On the Internet, a hostname is a domain name assigned to a host. It is usually a combination of the host's local name and the name of its parent domain. For example, in the URL fr.wikipedia.org, the hostname is fr and the domain name is wikipedia.org. 

Hostnames are translated into IP addresses through local host files or DNS. A person may have several hostnames. If a domain name does not have an IP address, it is not a hostname. Therefore, all hostnames are domain names, but not all domain names are hostnames.