A section of an address (URL) that tells you the kind of computer on the Internet with which you want to interact. There are a number of recognized domains. In addition to the ones listed above: .com (commercial businesses).edu (educational institutions).gov (government organizations).mil (military organizations).net (network organizations)
that which follows the at sign in an email address. For example, the domain name SiteLocationAssistance.com following @ is the extension that targets the website's unique address on the World Wide Web for email delivery. See the Guide to Effective Email by Kaitlin Duck Sherwood at http://www.webfoot.com for more information. Also, It may be worthwhile to see the definition of spoofing in the glossary S-file. definition of domain name extension defined how is a domain name spoofed What is a domain name extension in an email address
Part after the dot in the domain name is a domain name extension. DotZero is an Australian registered domain and so it has a .com.au extension. There are many other domain name extensions such as .com .net .org .gov .edu .info and many others.