Which part of a book helps the reader navigate different sections?

The table of contents serves as a crucial tool for navigating a book, as it provides an organized outline of the chapters and sections along with their corresponding page numbers. This enables readers to quickly find specific information or chapters they may be interested in, facilitating a more efficient reading experience.

In contrast, the index typically appears at the back of the book and lists topics, terms, or names along with their page numbers, but it does not offer an overview of the book’s structure. The glossary serves as a reference for definitions of terms used within the text, which is helpful for understanding specific language but does not assist in navigation. A summary offers an overview of the book's content but does not provide structural guidance for locating particular sections. Therefore, the table of contents is the most effective part of a book for helping a reader find their way through its different sections.