The first thing you need to learn about working with Word is how to use Styles properly. They make complex document construction and maintenance a snap. Start with:
http://www.addbalance.com/usersguide/styles.htm

For a basic understanding of how a Word Table of Contents (TOC) field works with Word's Heading Styles, see the attachment at: https://www.msofficeforums.com/word/...html#post16114.
Note how the Table of Contents also hyperlinks to the relevant headings. This is just one example of how using Styles facilitates document creation & management - edit/delete/add a heading, then preview the document and the Table of Contents updates itself!

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]