A "keyboard accessory" refers to any extra item or device that can be used with a keyboard to enhance its functionality or improve the user's experience. It could be something like a wrist rest, a keycap set, or a keyboard cover. Full definition
An optional keyboard accessory sticks to the tablet like a glue and offers durability and reliability to the overall package. (techtree.com)
The keyboard's F - keys also let you control things like volume and screen brightness, which you don't tend to get with a third - party keyboard accessory. (trustedreviews.com)
Two optional keyboard accessories will also be offered apparently, one aluminum and one leather. (vrzone.com)