A parked domain is simply another domain which you can use to access the SAME content as another domain. As an example:
You have two domains yourdomain.com and mydomain.net
yourdomain.com is the main domain for your website and you also want people to be able to access the site as mydomain.net, and have them both show the same content.
You can add the "parked" domain from within your Control Panel
Now when someone uses either yourdomain.com or mydomain.net they will go to the same website.
