There are many different types of ignition systems. Most of these systems can be placed into one of three distinct groups: the conventional breaker point type ignition systems (in use since the early 1900's); the electronic ignition systems (popular since the mid 70's); and the distributorless ignition system (introduced in the mid 80's).
The automotive ignition system has two basic functions: it must control the spark and timing of the spark plug firing to match varying engine requirements, and it must increase battery voltage to a point where it will overcome the resistance offered by the spark plug gap and fire the plug.
The first step in understanding a vehicle's ignition system is to learn about basic electricity. For more information on electrical circuits, how they work and how to troubleshoot them, please refer to the information on "Understanding and Troubleshooting Electrical Systems" elsewhere in this manual.