iBooks Author: template
A template is a predesigned set of elements for creating a book—sample chapters, various page layouts, and so on.
When you create a book in iBooks Author, you choose a template from the Template Chooser. Templates are optimized for viewing on iPad in either landscape (horizontal) or portrait (vertical) orientation.
Although you can modify individual book pages however you like, you can’t switch a book to a different template after you begin creating your book.