A parked domain name lets you mirror the same website as your primary domain name.  This can be useful when you may own several domain names and you might wish to use just one website.

Alternatively, you can setup the parked domain name to show the website that is in a sub-folder inside your public_html/ folder.

The other alternative is using that parked domain name to redirect to another website while you can use the domain for e-mail accounts or e-mail forwarders.

1. When you are logged into the cPanel control panel, click on Aliases icon
   
   
2. Enter in the domain name that you would like to park in the Create a New Alias domain text box
   
   
3. Then click on the blue Add Domain button

Once the domain name has been added as an Alias, by default it will mirror your primary website.  You can modify it to redirect to another website or to another sub-folder.