A common question that's not easily answered, is the defining factors between an Addon Domain and a Parked Domain in cPanel/WHM.
Here's a chart to help simplify the differences:
|Characteristic||Addon Domains||Parked Domains|
|Main domain appears in the address bar||Yes||No|
|Apache directive used||VirtualHost||ServerAlias|
|Treated as a subdomain (other than URL)||Yes||No|
|Ideal for multiple domains sharing the same address||No||Yes|