The Thumbnails pages are used in the gallery to display the thumbnails. Usually they have navigation menu that allows you to navigate through the entire gallery quickly. Also most of the built-in templates allow you to add header and footer text to the pages and an optional link back from the gallery.
How to change the number of thumbnails per page
Thumbnails pages file name
How to add a link back from the gallery to the thumbnails pages
If you have a question that is not covered in the above topics, please do not hesitate to ask our support team at firstname.lastname@example.org.