Normally for perfect binding in brochures printing and photobooks printing, the covers will be made from a slightly firmer/heavier paper/floppy card board. These will then sandwich the interior pages of your perfect binding which will normally be a simple plain paper or sometimes a slightly glossy paper. Normally these sections are then glued together using a very strong but also flexible glue in order to hold them in place, but the glue will be down the side to prevent it from gluing the pages shut. Normally the pages will be specifically cut using a rough cut along the back of the pages in order to encourage them to absorb more glue, while the other three sides will be face trimmed.

This then means that your perfect binding has the book or brochure bound down the side where the edges of your pages will be glued together to allow the book to be opened and closed while holding the pages in place.