Electrical System  

The electrical system consists of the battery, alternator, distributor, spark plugs, and ignition wires.  The purpose is to provide  source of electrical energy to start the engine and keep the engine running.  If the charging system stopped working, the battery's charge would soon be depleted, leaving the car with a "dead battery." If the battery is weak and the alternator is not working, the engine may not have enough electrical current to fire the spark plugs, so the engine will stop running. 
If the battery is "dead", it does not necessarily mean that there is anything wrong with it. It is just depleted of its charge. It can be brought back to life by recharging it with a battery charger, or by running the engine so that the alternator can charge it. Have your complete electrical system checked out the next time your vehicle is in for service.