A domain name identifies your business and reinforces its branding, much as your company name and slogan do. If you are using the free 6MB webspace that comes with all standard EarthLink accounts, you are not using your own domain name. But to be taken seriously, your business needs to establish its own identity online. But a domain name is at the core of every URL, the unique Web address that locates every Web site. The earthlink.net part is the domain name.
Domain names are unique, and many names are already taken.
Thats why, if you think you might want one, you should get one fast, while you have more options. If you search for a domain name and it is still available, it is very easy to have EarthLink register the name for you and then host your Web site. Thats up to you. If possible, companies and organizations also like to register generic names or keywords that relate to what they do. If you search for a name and it is already taken, try searching for variations of the name.