Your organization's Internet domain is the unique name that appears in the URLs for your web sites and after the @ sign in your users' email addresses. It often takes the form of your organization's name and a standard Internet suffix, such as google.com or stateuniversity.edu.
Your Google Apps customer account uses your organization's Internet domain. Users get access to Google Apps by signing in to their user accounts on your domain. The domain you use when you sign up for Google Apps is known as your primary domain. (Learn more about choosing your primary domain.)
You can associate multiple domain names with your Google Apps accounts, as long as you own the domain names. If your organization owns multiple domain names, see Manage multiple domains.
Google doesn't register or host domain names. If you want to use Google Apps but you don't have a domain name, we've partnered with a select group of domain registrars (available in US English only) to help you register a new domain.