"What is a domain name and how does it work?"
A domain name is a unique name that can be entered into a browser to resolve the numeric address (called the IP address) of your web site or email server. It takes the form of a name of your choice coupled with an extension relating to the type of site. Current popular gTLD ("generic Top Level Domain) extensions are .com (meant for business sites), .org (meant for non-profit organizations), and .net (meant for internet service providers). The original uses of the extensions broke down during the mid 1990s, and there has not been any attempt at enforcement since then. For example, it is now popular for people to register their family names as a .org, .biz, .info, .name. A complete domain name looks like this:
Notice, www is not a part of the name. The www is a computer resource. In fact it has become a convention used to imply the address of a world-wide-web site. The www is programmed into DNS by your hosting service after you have registered your name. You are not limited to www. The beauty of the system is that you may use or assign any prefix, or several, to your domain name which allows you to potentially have an unlimited number of web sites, email servers, dns servers, or news servers at any number of locations using your single domain name. Consider the possibilities of names such as sales.domainname.com home.domainname.com mail2.domainname.com
In an e-mail address, the domain name follows the @ symbol, so that your e-mail address would look like firstname.lastname@example.org.
A domain name can only be used by the one entity that has properly registered and paid for the use of that name.