Stories in Word
http://blogs.msdn.com/microsoft_office_word/archive/2008/10/02/behind-the-curtain-stories-in-word.aspx

Microsoft
2008

Abstract:

To Word, comments, the body of your document, footers, etc. are basically the same. And this is good because if a feature works in one story, there's a very good chance it works in all stories. This is why you can track changes in not only the body of your document (i.e., "main story"), but also in headers, footers, endnotes, text boxes, etc. Put simply, this common story architecture enables as much Word goodness in as many places in Word as possible.