Bible commentaries are often written by theologians and scholars to provide explanation and interpretation of biblical texts.
Commentaries can begin with introductory essays that give background and other information. Then the remaining text is organized by chapter and verse of the biblical book. Some commentaries include a Scripture Index which identifies additional pages in the book containing commentary on specific chapters and verses.
The Walsh library has thousands of books of commentary available for checkout. They are arranged in the order of the books of the Bible on the shelves in the upstairs section of the library with Library of Congress call number "BS". Here are some major series: