If a book is long enough to include chapters, then a table of contents will likely appear at the beginning of the publication. The TOC provides a sequential list of a book's organizational structure -- most commonly denoting each chapter's number, title and starting page location. The chapter titles listed in the TOC can help guide readers in finding specific sections; when the chapter titles don't provide specific enough detail, readers may need to consult the index found in the back of the publication.
Origins of the Table of Contents
In the late first century, the Roman Pliny the Elder purposefully included what we now call a table of contents in his "Natural History" to spare the public from all trouble, and so that "one may search for what he wishes, and may know where to find it." Pliny in turn credits the literary innovation "which has already been done among us" to Valerius Soranus for his work entitled "On Mysteries."