A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electro-chemical reactions . If you look at any battery, you'll notice that it has two terminals. In a large car battery, there are two heavy lead posts that act as the terminals.
Electrons collect on the negative terminal of the battery.
Normally, you connect some type of load to the battery using the wire. The load might be something like a light bulb, a motor or an electronic circuit like a radio . Inside the battery itself, a chemical reaction produces the electrons. Electrons flow from the battery into wire , and must travel from the negative to the positive terminal for the chemical reaction to take place. Once you connect a wire, the reaction starts.