A domain name is a website name that has an associated IP assigned to it. Humans would have a very hard time remembering all the IP numbers to visit places on the internet so the domain name is a way of assigning an associated name with one particular IP address so we as humans can simply type in a name instead of several numbers. The syntax for a domain name is: websitename.extension. Domain names are used to identify a website, brand, service, or product. When a visitor types the name of a domain, they will receive information back from a server of the IP address of the website that they wish to visit, and then their computer will go to that particular web address. There are many extensions and they are adding more often. A few extensions are:
A .com name is the most common. For more information see: http://en.wikipedia.org/wiki/Domain_name.