Domain names are composed of at least two levels, a top-level domain and a second-level domain. The top-level domain, also referred to as TLD, is the suffix or extension attached to Internet domain names. There are a limited number of predefined TLDs, such as .com, .net and .org.
A second-level domain (SLD) is the portion of a Uniform Resource Locator (URL) that identifies the specific and unique administrative owner associated with an Internet Protocol address (IP address). The second-level domain name includes the top-level domain name. For example, "mydomain.com" is a second-level domain, as it includes the domain name "mydomain" and the top-level domain "net."
If you need to further distinguish your second-level domain name, you can use a third-level domain name, such as "webhosting.mydomain.com."
When a third-level domain name points to subdirectory in your current site, this is referred to as a "subdirectory domain name."
To create a subdirectory domain name:
In ControlPanel, click the Manage Services tab and then click the Website icon
Scroll down to the Added Functionality section and click Subdirectory Domains.
The Subdirectory Domain Summary page lists any active subdirectory domains that have already been set up for your domain. When the Add Subdirectory Domain Name page appears, carefully review the restrictions and information about any additional fees that may apply.
In the Subdirectory Domains page click Add Subdirectory Domain.
Enter the name of the subdirectory domain you want to create.
Click Add to create the specified subdirectory.
In the Purchase Subdirectory Domain page, click Purchase Now.
A Subdirectory Domain Confirmation message appears.