A power bank is a portable device that provides emergency power to your electronic devices such as smartphones, tablets and laptops. It stores energy from an external source, like a wall outlet or solar panel, and then releases it when you need it. Power banks are becoming increasingly popular as they offer more convenience than traditional charging methods. They are also great for people who are always on the go and need to keep their devices charged up. In this article, we will look at how power banks work and why they are so useful.