You might want your sub domain to redirect to another page. To accomplish this, please do the following:

1. Login to your cPanel.
2. Click the Subdomains icon.
3. Make sure you have already added a subdomain to your account.
4. At the bottom, click the Manage Redirection link to the left of the subdomain which you would like to redirect.
5. In the box, type the URL (http://domain.com/optional-stuff) for which you would like a user to be redirected to if they go to the subdomain.
6. Click the Save button.

You have now successfully created a redirect for a subdomain. When you visit the subdomain, you will be redirected to the desired page.