Induction - Magneto / Flywheel
The magneto is a device used to create a large potential difference capable of creating a spark to "fire" the combustion of gasoline in an engine with no battery. These are typically found on lawnmowers, weed eaters, chainsaws, mopeds and other small engine devices. A magnet is embedded in the flywheel on the engine. A coil is placed near the edge of the flywheel so that as the flywheel goes around, the magnet passes by the coil. This creates a rapidly changing magnetic field which induces a current in the coil. The potential difference across this coil is not usually enough create a spark in the spark plug. To make a bigger potential difference, the first coil is used as a primary coil and a secondary coil is used with many more windings than the primary. This results in a step-up transformer which produces enough potential to cause electrons to jump the gap on the spark plug.
This view is slightly simplified, as a few devices have been left out of the explanation. A few devices (points, choke) are used to control the timing of the spark. They however are not directly related to how the spark gets created.