The art and craft of bookmaking long predates photography as an expressive medium. Like any discipline, book design/publishing comes with its own nomenclature. Below are some common terms that you may encounter when you begin making and publishing photo books.
Accordion (Concertina) Fold: Parallel folds that open up like an accordion.
Addendum: Information added to the end of a book after publication.
Appendix: Supplemental information added to the end of a book (tables, glossary, bibliography, etc.).
Awl: A tool used for piercing paper