If you’re one of the sellers who are listing in the categories which have mandatory use of eBay catalogue data then there’s a useful eBay document you should read. The document covers both the (Link opens in .pdf).
Understanding the search experience buyers will be presented with is key to making best use of catalogue in these categories which are already MP3 Players and GPS Systems and the categories being added are Mobile Phones, Video Games Consoles, Photography subcategories Digital Cameras, Film Cameras, Camera Lenses, Tripods and Flash Units.
All sellers need to update their listings in these categories, including any Good Til Cancelled listings, buy the 17th May. If you don’t then your listings are likely to receive much lower exposure in search results. It’s also worth remembering that Subtitles will not be visible in some search result pages, but will still be visible on the View Item Page.