This is why we use "folio" to refer to:
* A sheet of paper: Especially a large sheet folded in half to make a page in a book.
* A page in a book: Often referring to a numbered page, particularly in a large or important book.
* A book or collection of documents: Especially a large and important one.
The word "folio" also gives us other words like "foliage" (the leaves of a plant), "foliate" (to form leaves), and "foliation" (the arrangement of leaves on a stem).