Definition - What does Magneto mean?
A Magneto is an electrical generator which uses permanent magnets to produce periodic pulses of the alternating current. It does not contain a commutator that produces direct current. It is a type of an alternator but is regarded different from other forms of alternators that use field coils instead of permanent magnets. They are never widely used for the purpose of large amount of electricity generation. They are advantageous as they are simple and reliable. But they are inefficient as they have weak magnetic flux accessible from their permanent magnets which reduces their use in high-power applications.
Petropedia explains Magneto
Magnetos are electrical generators used for producing alternating current by using permanent magnets. They are commonly used as an ignition Magneto, small engines like chainsaws and in spark-ignition of petrol engines. They are used in aircraft engines that keep the ignition separate from the rest of the electrical system which ensures that the engine will continue working in the event of a battery or alternator failure. They were used in the isolated power systems like lighthouses, arc lamp systems in which the simplicity of Magneto was an advantage. They are not used in the generators that are connected to the electrical grids for the power generation of central station.