An add-on domain is a seperate and unique website. An example of this is: you own yourdomain.com and decide you want another website at yourdomain2.com. This website is a completely different type of site from yourdomain.com so you create an add-on domain.

A parked domain is a domain that sits on top of your current website. So, let's say you own yourdomain.com and want to secure yourdomain.net so nobody else registers your company name. You setup yourdomain.net as a parked domain so that when you goto yourdomain.net it shows the website at yourdomain.com.

To view how many of each you can get check out the packages page. If you would like to setup an add-on or parked domain please submit a help desk ticket via your account center.