A Battery can be one "cell" or many "cells". Each cell has an anode, cathode and electrolyte. The electrolyte is the main material inside the battery. It is often a type of acid, and can be dangerous to touch. The anode reacts with the electrolyte to produce electrons (this is the "negative" or "-" end). The cathode reacts with the electrolyte and takes electrons (this is the "positive" or "+" end). An electric current happens when a wire connects the anode to the cathode, and the electrons move from one end to the other. (But a battery can be damaged by just a wire connecting the two ends, so a "load" is also needed between the two ends. The load is something that slows the electrons down, and usually does something useful, like a lightbulb in a flashlight, or the electronics in a calculator). 