The car battery, like all batteries, produces electricity thanks to a chemical reaction that occurs between the acid liquid it contains and the metal it is made of.
There are different types of batteries. The lead battries which are the most common have a certain weight and can be recharged using a common charger. Through this procedure you will in fact restore the surface of the metal in contact with the liquid which will be able to generate more energy.
Lithium car batteries are also entering the market today. This allows you to create batteries of the same power but with contained dimensions and weights.
The problem with this new technology is the cost which is still very high today.
When replacing old batteries, do not dispose of them in the environment. They could in fact cause a lot of pollution. Put them in the appropriate landfills, they can be recycled.