Subdomains are a way of creating separate accounts within your master account, which are accessed as separate URLs.
Practically, a subdomain is a sub folder within the public_http level of your account that has it's own cgi-bin directory. The "timber" example above creates a new top-level folder called timber, with a cgi-bin sub-folder. Upload your files for the subdomain to this location, including a separate home file (such as index.htm).
Currently you cannot create e-mail accounts with the subdomain extension. A workaround for this is to create an account called "email@example.com", or similar.
To add a subdomain:
Click on the Subdomains button on the home page.
Note: You can only successfully create a new subdomain once your DNS number has successfully propagated for this account.
Enter the text for the new subdomain in the field in the available field. You must conform to domain name conventions for the addition to the name.
Click on the Add button. A folder with the same name as the subdomain has now been added to your public_html folder, with a cgi-bin sub-folder (if CGI scripts are enabled on your account).
There is a few hours of propagation while the subdomain saturates throughout the internet.