Subdomains are a way of categorizing different section of your website content, with shorter and easier to remember URLs for your website visitors. For example, you can set up a "cat" subdomain on your master account "mypetshop.com", which your webswite visitors can easily entered in browser as "cat.mypetshop.com", which is the cat's section for your website. Generally, large product website uses subdomains to establish branding and focus on separate product lines. Subdomains are setup and manage through your master CPanel hosting account control panel.
In practical, a subdomain points to a subfolder within the public_html folder of your web hosting account that has it's own cgi-bin folder, this configuration is done during the setup process of the subdomain. The "cat" example above creates a new subfolder cat, with a cgi-bin folder within. You can then upload files for this subdomain to into this folder.
Creating email accounts with the subdomain is not possible for the current setup. However, there is a workaround for this, you can create an email account named "firstname.lastname@example.org" to distinguish the email accounts from others.
To add a subdomain:
Click Subdomains button on domain hosting account control panel.
Note: You can only able to create a new subdomain after your domain nameserver has successfully changed and propagated.
Enter the new subdomain name in the subdomain name field. The name entered must conform to domain name convention otherwise the process will fail.
Click Add button. The setup process will create a subfolder with the same name as the subdomain in public_html folder, with a cgi-bin subfolder within, and configure webser to recognize the new subdomain name and that it is pointing to this newly created subfolder.