When creating a ASP.NET MVC Project in Visual Studio 2010 , one might notice the Web.config file has additional 2 files
What are the difference between Web.Debug.config and Web.Release.Config in ASP.NET MVC Project ?
This is something new in Visual Studio 2010 and higher versions . It is called “Web Deployment’s Web.Config Transformation” feature.
You could have the settings specific for an environment like debug or production.
Know more about the Web Deployment’s Web.Config Transformation feature from MSDN Blog