Sub-domains are useful when you have a sub-section of your website which is separate from your main site, such as when you have a blog or when you are setting up a new development site for staging. A sub-domain uses the format something.yourdomain.com. They work in exactly the same way as a full domain, and can have their own FTP users, applications, PHP configuration, DNS setup and log files (as well as all the other features of full domains).
To set up a new sub-domain on your account follow the steps below:
Sub-domains can be accessed with the same FTP account as your main domain. For example, if your main domain is test.com and you create blog.test.com, you can manage both domains with the main FTP account for test.com. You can also create additional FTP accounts by clicking on Websites & Domains > FTP Access.
Note: when creating a new sub-domain it may take 10-15 minutes before it will start working when you type the new address into your browser (due to the time it takes for DNS updates to take effect).