Parent portals are sites that are defined by a unique URL (www.CoffeeConnections.net,www.e-coffeehouse.com, etc.). Parent portals allow you to run multiple sites from the same host and same DotNetNuke installation. This means that each domain name is unique but points to the same location. DotNetNuke handles how to route the requests depending on which domain name is entered.
Child portals, on the other hand, are sub-portals related to your main portal and share the domain name of their parent. A directory is created on your web server allowing the portal to be accessed through a URL address that includes a parent name and the directory name combined (say www.CoffeeConnections.net/TestingPortal.)