What is a domain name?

A domain name is an address for the Internet. It helps people find your web site. Just as homes and businesses have street addresses, all web sites have domain names. The Yahoo! domain name is yahoo.com.
A domain name is made up of two parts, typically preceded by www. Let's use yahoo.com as an example:
The first part, yahoo, is a unique name that represents the web site.
The second part, com, is the extension, and stands for "commercial." There are many extensions available, though .com, .net, .biz, .info, and .us are the most popular extensions in the United States.