In the most simplistic terms, the battery is a device that converts chemical energy into electrical energy. Today’s batteries like AA, C or D batteries have two terminals or ends. One is a (+) or positive terminal and one is a (-) or negative terminal. The interior of the battery has components that act like the Voltaic pile using a variety of different components, but all having metal for the electrodes and some sort of brine-like material for the electrolyte. The electrodes do not touch each other but are electrically connected by the electrolyte.

When you connect a wire between the negative and positive terminals, the electrons flow from the negative to the positive terminal. When something like a light bulb or electrical device is wired to the battery, it can be powered by the electron flow (i.e., electric current).

The electrical force across the terminals of a cell is known as the terminal voltage and is measured in volts. The force or the voltage is dependent of the chemical reactions inside the cell so using different chemicals can produce differing voltages.