Lets start off with a few basic pieces of knowledge to get people who don’t know what DotNetNuke is up to speed.
DotNetNuke (DNN) is an open source Content Management System designed to get your mind off the usual basics of site creation (User Management, Permissions, Caching, layouts to a certain extent) and let you focus more on the content aspect of your site. DNN also has a modular design of the site, meaning each control developed for DNN will (usually) work independently of each other and can be placed on any page of the site you are creating.
OpenWebStudio or OWS is also open source and is installed as a regular module into DNN. once installed, OWS becomes a tool for the sites super users to use to rapidly create their own modules.

OWS IDE
OWS not only gives developers direct access to the database from the presentation layer of the web application but also give you the ability to send emails, update the user profile, consume web services, RSS feeds and much, much more.
When you combine DNN with OWS you can create web applications in less than half the time it takes to create an application writing code in strictly in .Net. You also have to keep in mind that any kind of code maintenance or new features will also take less time, In .net you might have to modify your Objects, DAL, BLL and also Presentation Layer for your modifications to take, then you will have to build your project, and push up the assemblies. Now, it might not seem like a lot of time, but with OWS, almost none of that is needed. Just modify your query:

Sample OWS Query
Then modify your templates using tokens defined by your query (they are simply in the format of [ColumnName]):

OWS Tokens
Thats all you need to do to make a simple modification to your module.
Also you should know that OWS is not the end-all be-all of module development. While we would like to believe this is it, there are still things that are better done in .net especially if you need as little overhead on a module as possible.
Yes, I realize I probably didn’t give you enough of an idea to actually start creating your own module using OWS, but some time in the future I will write a little post detailing how to create a simple CRUD interface using OWS. All in all I hope this is a good overview to give you an idea of what DNN and OWS mean for web development and what it can help you with on your site.