Taking Control of Your Table of Contents or Document Map
http://blogs.msdn.com/microsoft_office_word/archive/2008/12/02/taking-control-of-your-table-of-contents-or-document-map.aspx

Microsoft
2008

Abstract:

Table of contents and the Document Map are designed to work best with documents that use styles. Styles not only apply a look and feel to a document, but also provide semantic structure. For example, applying a Heading 2 style to some content that exists under a Heading 1 style implies hierarchy within a document.