DotNetNuke is a web content management system based on Microsoft .NET. The Community Edition is open source.
DNN Platform (formerly "DotNetNuke Community Edition" content management system) is open source software that is intended to allow management of websites without much technical knowledge, and to be extensible through a large number of third-party apps to provide functionality not included in the DNN core modules. Skins can be used to change the look of a website using DNN.
The default functionality of DotNetNuke can be expanded by adding third-party modules, either from an existing library of modules, or through in-house development of custom functionality. The DotNetNuke framework provides basic functionality such as security, user administration and content management, while modules are used to tailor the web site for specific deployment needs.