I'm reading through a fantastic article on the .NET Configuration namespace (found here) which talks about creating custom sections, elements, collections, widgets, and flying toasters. The only complaint I have is that the article is only technical and doesn't provide any conceptual context. MSDN doesn't appear to have much conceptual information, either.
So can someone explain, please, what a "section" is, what an "element" is, and when it would be appropriate to use each?