Power Banks. A Power Bank, is a portable battery/portable charger.
This means that you can have it with you and charge your devices when you are in a place that is not easy to access power or you do not have a power charger with you or you are outdoors, outdoors, on the beach, etc. The operation of a Power Bank is very simple! All you have to do is first charge it on a USB charger. E.g. the same charger with which you charge your smartphone or in the USB port of a computer/laptop). This is how the Power Bank will store energy in its built-in batteries. Then connect to the powerbank that gadget needs charging!