12 volts DC
The starter on a car requires a lot of electrical current to rotate the engine fast enough for it to start. When the car's battery doesn't have enough electricity to do this a battery from another car or another source of electrical current can be supplied (jumpered) to the car to "jump start" it.
DC aka direct current
D.C. current is the only current used in your car. If you jump a battery from another battery, that's D.C.
The smallest engine used to build a car was found in the 1962-65 Peel P50 at 49 cubic centimeters. The smallest engine found in current product cards is the 2008 Tata Nano.
Jump starters are used to jump start a car when the engine will not start by itself. It is a common reason for car breakdowns and all breakdown companies have jump starter tools.
Your question contains the answer. It is used to store electrical energy. This energy is used to start the car and run the engine and all electronics.
This depends on many factors, such as the size of the generator engine, for example. It is basically like the starter motor on a car engine.
You start the engine in neutral.
How many types of electric current are there ? Are you talking about AC vs. DC ? The car's battery supplies DC, just as all batteries do. The DC from the battery is used to turn a small but powerful DC motor, and to energize a solenoid that pulls the powerful motor into contact with a mating gear on the engine, enabling it to crank the engine in hopes that the engine may kick in and begin to run on its own. The DC current that the battery supplies while the little "starter" motor is cranking the engine is quite considerable, and may range upwards of 100 amperes!
you engine
??? Huh?
The 'starter' actually turns the flywheel, enabling the car engine to start. The 'alternator' supplies AC & DC current to the electrical components of the engine and vehicle.