Web.config Transformation Features in Visual Studio 2010

When developing applications in Visual Studio, I normally pay a lot of attention to my Solution Explorer. However, I recently spotted something that I didn't notice before. Well, at least something that I haven't paid attention to! In Visual Studio 2010, if you click on the Web.config file and expand the node - there are two extra files - Web.debug.config and Web.Release.config. Now if you open them you will notice that they contain XML that is similar to your normal Web.config file.