Domain Name

It's also useful to understand the different parts of a URL, which is comprised of parts called "domains." The chief domains of a website are its host name, second-level domain, and its first-level (or top-level) domain.

Let's use the components of the That Network home page URL as an example.Host name. The That Network URL is www.thatnetwork.com. The host name is the "www", which is short for the World Wide Web. This means this web page is hosted on the World Wide Web.

Sometimes you'll see the "www" is not there and replaced with a different host name. For example, the popular search engine and website portal Yahoo! has different host names for its features. Yahoo!'s Finance section, for example, resides at http://finance.yahoo.com, and its Games section is at http://games.yahoo.com. This means these two parts of the massive Yahoo! website reside on different hosts.

Second-level domain. In our initial example (www.thatnetwork.com), the second-level domain is "thatnetwork". This is often informally referred to as a website's "domain name," although the term "second-level domain" is technically correct.

This is the part of the domain name that identifies the business, organization or other entity operating the website. It's, if you will, the "brand name" of the website. Each second-level domain, combined with the top-level domain, must be unique. That is why registering a second-level domain is required. See Registering a Domain Name for more information.

First-level (top-level) domain. The first-level domain follows the second-level domain and is designed to describe the type or location of the website. In our example, the first-level domain of www.thatnetwork.com is "com". COM, short for commercial and often referred to as "dot com," is the most-common first-level domain, and you will see it wherever you go on the Web.

Other popular first-level domains are ORG (organization), MIL (military), EDU (educational institution), and NET (network). In recent years, new first-level domains have been approved, including BIZ (business), AERO (aerospace) and TV (television). There are also two-letter first-level domains for each country. A complete nation list can be found on the Internet Assigned Numbers Authority website at http://www.definethat.com/reference/countrycodes.asp.