The electric battery that supplies electric energy to your car is general called a car battery. The most common type of car battery is the lead-acid batteries. They provide a 12 volts potential difference by serially connecting six 2 volts cells. The battery consists of plates of lead and lead oxide submerged into a solution called electrolyte solution. Electrons are released because of the chemical reaction which allows them to flow through conductors and thereby producing electricity.
Most modern car batteries are maintenance free, but if you have an older type you may need to do a top up from time to time. The top up is done by removing the tops and top up the cells with distilled or deionised water just above the visible plates. Make sure you have the right kind of water since tap water or rain water will impair the battery performance.
In most cars the grounding is provided by connecting the battery's negative electrode to the car's body. When you remove the battery on your car you should remove the ground connection first and then the other connection. When you connect the new battery you should connect the positive connection first and then the ground connection.