Yes, DNN is a largely empty framework that among other things, provides security and template management for any of the modules that you decide you want to install into it.

Have a browse around the Marketplace (button above on this site) or snowcovered.com to see what sort of modules are around. There are also plenty of free modules, and around a dozen are included in the installation package. The discussion forums for those modules are part of this forum we're in now.

"Portal" is a term that was never well-defined and in the case of DNN it simply refers to a website. A single installation of DNN can run any number of websites or portals. This is one of its more powerful features.

Rob

Crispen:

To add to what has been said, notice that you do not need to buy any modules to get started, you understand that right?  DNN comes with a bunch of modules to handle the basic design of the Web site.  Your basic module is the HTML/Text module which, together with the menuing system, will let you create a very functional site very quickly.  This, and the use of "Skins", is what makes DNN great.  The third party modules and skins, free or commercial, are there to satisfy specific needs and functionality that cannot be achieved by the basic modules alone.  The use of the FCK rich text editor by default is pretty cool too.

Also notice that because of the modular nature of DNN you can add third party modules and skins on the fly without having to take the site down, restart, or recompile the core code.  (These facts are not mentioned frequently enough).

Carlos