This keyboard coating "gum" is equipped with a battery for a very long battery life (3 months after the manufacturer), enough to see it coming. Charging is done with a micro USB charger connector or cable (not supplied.)
In use, and despite the compactness of the keyboard (24 cm long), typing, smooth, precise and surprisingly nice for this kind of keyboard. It's convenient, and it is even much more if it is equipped with a stand for the tablet or phone - it's actually almost essential. In these conditions, it is quite possible to work on Word for example (it's good, Office is now free.)
High price, but flawless finish.