What is a master page rule?

Product: Quark Publishing Platform (QPP) NextGen, QuarkXPress

A master page rule is a set of master pages arranged in accordance with how you want to produce a multiple-page output. Like a master page is a template for a single-page output, a master page rule is a template for multiple-page output with different layouts.

For example, if you have a multiple-page document (a chapter in a book) and you want to use the layout of master page A for the first page, master page C for the last page, and master page B for the rest of the pages, you can define these rules by creating a master page rule out of master pages A, B, and C.