A domain name is a word or phrase that is combined with a TLD to uniquely identify your web site. In basic terms, the domain name is simply the name of the site, including the letters after the dot.
The root of the domain name is followed by a TLD (top level domain) extension, which usually indicates the nature of the site somewhat. A .com TLD is short for commercial, which indicates that the site is for commercial use. There are dozens of TLDs currently available, with new ones being created each year. Domain names are basically the identification cards of the internet because they allow visitors to find your web site without memorizing long terms or IP addresses.