Certified DNN Partner helps with explanation
How to Create a DotNetNuke / DNN Portal
DotNetNuke (now called DNN) portal systems have a variety of useful features. A portal is simply a site used as an entrance point to reach the World Wide Web. The DotNetNuke, or DNN portal is powerful and has many useful features. We will explain how the DNN portal works, and define parents and client portals.
Most shared hosting methods require you to buy a domain name, and host with an internet provider. If you want to buy another domain name, you need to get an additional hosting package; this can prove to be costly. Many organizations use DNN portals for their business. The multiple DNN portals enable individuals to manage multiple domain names from just one hosting account. All the administrator has to do is create a portal for each domain name. To create DNN multiple portals for domains, go to the portal alias settings, and select the domain name you would like to point to the portal.