Table of Contents in a document is an important element that keeps readers and authors organized. It allows you to create a list of links at the beginning of your document that point to different sections of that document. Once created your table of contents, you can easily update its links as you edit each section of your document.
To make a table of contents, you need to mark each section of your document with a heading. To do this, highlight appropriate text, and then select a heading size from style menu in the toolbar. To revert a heading to normal text, simply select Normal option from same drop down menu; doing so will also remove that link in toc after you update the toc. You can then add a toc from Insert menu. After you've added a toc, it'll automatically create a link to each heading in your document. As you update your document, you can easily update the toc by clicking Update now button in top right of the toc.