Sounds dangerous doesn't it ?.. We'll it isn't !
DotNetNuke is a .NET framework for creating fully functional dynamic websites without the need for hiring a delevoper and without knowing a stitch of HTML, ASP, .NET or any other web programming language.
Your DotNetNuke website visually relies on a "Skin" which gives the whole site a specific look and feel. Skins can be written especially for you for around £200 or you can purchase many great looking "off the shelf" skins for around £50.
Once you have your DotNetNuke skin in place and your site's general appearance how you want it, you then just need to add the site content. Again this is done without using any programming by utilising DotNetNuke's built-in "Modules". There are modules to cover all manner of tasks from simple text and pictures to feedback forms, FAQs, document lists, calendars, RSS newsfeeds, etc, etc. DotNetNuke also supports user databases whereby certain users can be configured to see certain parts of the site that other users can't, of indeed see the whole site in a very different way altogether.
All site management including adding and updating content is done solely with a web browser and nothing else !
Behind the scenes, Microsoft .NET looks after the site formatting whilst Microsoft SQL Server looks after the site content.
In short, DotNetNuke is a very powerful but very simple website creation tool.
This entire website you are currently looking at was completely created in DotNetNuke in approximately a tenth of the time it would have taken to write in HTML, with at least 100 times the functionality !
What to know more ?... Have a look at the official DotNetNuke Project Guided Tour Website