Such a section of 16 or 32 pages when folded with yarn tied together we call stitched sewn, or the spine of the book will be machined off after folding the various sections of the book and then glued into the cover, this is called perfect binding.
Also read the article: What is the difference between a sewn, adhesive or bound book?

Thicker types of paper are harder to fold than thinner types of paper. Try for yourself folding a postcard 3 or 4 times (booklet of 32 pages folded 4 times).
Choosing heavier and thicker paper most people choose a finish of 16 pages. After printing the section is then cut in half, and then processed as two sections of 16 pages.
Finally the result of the spine of the book looks nicer, but its also more expensive because the number of quires that must be processed are doubled.

Papers as 90 and 115 grams mc, and 90 and 100 grams woodfree offset can be finished very easily to booklets of 32 pages. For that reason we recommend using papers as HVO 120 grams and 90 grams novel paper to finish booklets of 16 pages, or a thread-free finish.