Subdomains are the third level domains that are used to organize your Web site content. They are just like folders under your root directory, with a special URL to access them.
To add a subdomain:
Note: The parent domain name, (displayed next to the text box) is appended to the subdomain name.
For example: Domain name 'mydomain.com' is appended to subdomain 'mysubdomain', thus a subdomain named 'mysubdomain.mydomain.com' is created.