Subdomains are subparts of your main domain name and allow to host a separate site in subdirectory of your domain and you can access it using different ways via browser.
To add sub domain name.
1. Login to your cpanel.
2. In “Domains” section.
3. Click on “Subdomains”
4. In Create subdomain name section place a domain name you want to setup as subdomain name.
You will find a box titled Subdomains, with your domain name after it. If you have more than one domain name, such as parked domains, or add-ons, you will find them here in a pull down menu. Select the correct domain for which you wish to make a Subdomain and in the box enter the prefix name of the new Subdomain.
The result should look like this:
something.yourdomain.com(or whatever your TLD is)
For example, 123abc.yourdomain.com
Below the Subdomain line is the Document Root line, and by clicking on the Icon, it will bring up the default directory for the Subdomain.
5. Now click on “Create’.