Following the update, players will be able to fill out collections in the achievements tab by finding, equipping, or consuming certain items. If you collect all of a collection set, then you'll get a reward chest for your trouble. Some collections will be visible from the start, while others will need to be discovered or triggered during the course of gameplay. When the patch goes live, the game will attempt to fill out collections retroactively, although it will not be able to identify every item looted in the past.
Due to this new category, ArenaNet is making some minor organizational changes to the achievement UI and will be renaming the bank collections tab "material storage."