It's a global tracking of most furniture items from the home shops around the game.
The catalog is divided into books based on the province (or special merchants), and each book is divided into chapters based on the type of furniture.
All chapters from a particular province will have the same number of maximum pages, though not all will have inventory listed. This is intended and a result of the storage mechanic used as a resource consideration. No need to bug it.
The catalog is self-updating based on your characters visiting the shops. As soon as any character has visited a shop and listed the items for sale (ORDER), that shop will be added to the catalog to be viewed by everyone. The initial release comes with a decent list of shops put together by those of you who tested it, but by no means is it complete. Further, each instance (Plat, TF, Prime) will maintain its own unique catalog based on visiting the shops.
The catalog only inventories furniture shops that you can use ORDER to list the available furniture. It does not include the shops for exterior customizations or any other oddities that may be out there.
For shops with rotating merchandise, such as Frother's in the Seacaves, only the merchandise available at the time it was first visited will be listed. This is intended for now, but may change in the future.
Go forth and redecorate with ease!
To discuss it in Plat, click here or in Prime, click here (not yet released in Prime but SOON!)