If you have captioned your figures, tables, and equations using Word’s captioning feature (see the Inserting Captions tab to the left of this Guide), you can have Word generate your lists for you automatically. This indicates that it is getting information from somewhere else. Notice that once the table of contents is in your document, it will turn gray if you click on it.
At any time, you can update it by right-clicking on it and selecting Update field. The table of contents is a snapshot of the headings and page numbers in your document, and does not automatically update itself as you make changes.
If you have used Heading styles in your document, creating an automatic table of contents is easy. All subheadings should use Heading 3, and so on. All major headings within your chapters should be use the Heading 2 style. If you want an automatic table of contents you need apply the Heading 1 style to all of your chapter titles and front matter headings (e.g. Microsoft Word can scan your document and find everything in the Heading 1 style and put that on the first level of your table of contents, put any Heading 2’s on the second level of your table of contents, and so on. An automatic Table of Contents uses Styles to keep track of page numbers and section titles for you automatically.