It's just a collection of links to different anchor points in the (x)html document(s).
Code:
<h3>Contents</h3>
<a href="../Text/book.html#chap001">Chapter One</a>
<a href="../Text/book.html#chap002">Chapter Two</a>
<a href="../Text/acknowledgements.html">Acknowledgements</a>
.
.
.
etc.
And the anchors in the document (if you don't have separate documents for each TOC entry) would be something along the lines of:
Code:
<a id="chap001"></a>
or
Code:
<h3 id="chap002">Chapter Two</h3>