Selecting an ebook start point changes the point at which the book will open for readers from the default, which is typically the beginning of the main body of the book.
If, for instance, you wanted the book to automatically open to the Dedication page of your book, you could select that as the start point. Note that the designated ebook start point may be overridden by some ereader devices. If you're unsure about whether to select a start point, we recommend leaving the start point unselected. Ereader devices will then revert to their default start point for readers.