A folio represents the document or collection of pages that you plan to print. You determine how to collect, store, access, and represent the pages in a folio--the folio is simply a repository for the pages. The folio creates a page iterator that provides access to the pages within a folio. The page iterator also establishes the order of the pages.
Folios are instances of classes derived from MPageFolio. All page folios have two important properties: They can print and they can create page iterators. The system provides several page folios, but you can also define your own.