I think most of these pages are described here in the Help Documents, but the information is definitely scattered, not all on the same page. 
It could be improved upon.
Also, these pages don’t all work the same way. Say for example that you don’t have a photos page. To create one, go to Pages and hit the New Photos Page button. (It only shows if there’s no photos page already.)
If you want a books page, however, you have to first create a page, again by visiting Pages and then hit the New Page button. Let’s name it “Currently Reading”. For now, it’s just an ordinary page. But, by visiting Bookshelves and tapping the little 
icon next to one of the shelves, you can include books from that shelve on the page you just created.