Just to add to the previous comments.

A battery is a collection of of stuff. I.E. "The doctor has me scheduled for
a a battery of tests to figure out whats wrong". For example your typical
1.5V "thing" is actually an electrical cell, however practically everyone
calls it a battery.

A car battery is 6 cells connected in series, the voltage of each cell adds
to the others and you get 12 volts. Each cell is really big so you also get
a lot of amperage.

Electrical current is measured several ways, the main two a

1. Voltage

How hard do the electrons want to move a.k.a. pressure; and

2. Amperage

How many electrons go by, a.k.a. volume.


Different cells develope different voltages, for example:

1. Lead acid - 2V
2. Carbon - Zinc ( generic battery) 1.5V
3. Nickel Cadmium ( NiCads) 1.2V

If you connect two car batteries in parrallel you still only have 12V but
you have more current which is measured in Amperes.