The package document is an XML document that defines the key aspects of an EPUB publication. It is used by reading systems to render an EPUB publication

The package document consists of three primary sections: metadata about the publication (title, author, publisher, etc.), a list of all resources (the manifest) and the order in which to present the content documents (the spine.

The page list is a navigation aid that provides access to static page break locations (i.e., to locations that do no change depending on the font and screen size).

The page list is particularly useful in mixed print-digital environments (e.g., in a school where some students may need an accessible digital version of a textbook), as it allows everyone to find the same location regardless of the format used.

While the page breaks usually correspond to a print edition or other statically formatted version of the publication, publishers sometimes add page breaks to purely digital works in order to facilitate coordination of locations (i.e., so users can get to the same location regardless of what reading system they use).

See resource.