While both book folding and pop-up books fall under the broad category of paper crafts and book arts, they are fundamentally different disciplines. Understanding the difference helps clarify what kind of tools and designs you'll need for each craft.
Book Folding
In book folding, the book remains a single unit. Pages are measured and folded back into the block of the book. The design is visible on the edge of the pages when the book is standing upright. You don't glue or assemble separate parts; you sculpt the existing book block.
Pop-Up Books (Paper Engineering)
Pop-up books involve cutting, folding, and assembling multiple pieces of cardstock or paper tabs that are glued into the gutter of a book. When the book is opened, the mechanical structure lifts the elements into a 3D shape. It requires precise glue points and kinetic mechanics.