What is a coil?

Answer

it convers 12 volts into 50,000 volts

Coil in electronics means wire wrap around some media the get different uses in applications. The above answer only pertains to coil on a car I suppose

It is part of the ignition system. in older cars, it is a single unit that is about the size of a coke can. In many newer cars, you have individual coil packs sitting on top of each spark plug.