A battery is a device that stores energy. Most of our cell phones, music players and even cars require energy in the form of electricity, and a battery can supply small amounts of electricity to these devices.

Batteries come in all shapes and sizes. The most familiar kind are conventional alkaline batteries (like AAA, C or D batteries), which look like small tubes. The rechargeable battery in a digital camera may be a flat disk. Watch batteries are small and round, and the heavy battery that provides power to a car usually looks like a giant block.

They may look different, but all batteries more or less work in the same way. Inside a battery are three main parts: an anode, a cathode and an electrolyte. You might think of a battery like a three-layered sandwich, where the anode and cathode are slices of bread, and the electrolyte is in-between them. (The electrolyte keeps them from touching.) Just as a sandwich provides you with energy in the from of food, a battery provides energy to electronic devices in the form of electricity.

The anode and cathode are called electrodes. They are charged plates, usually made from metal. One of them has a negative charge and the other has a positive charge. When you use a battery, you connect the negatively charged plate to the positively charged plate, and the negative charge starts to move through your device. This moving charge is called the current, and the current delivers electricity.