What are dynamos?

Answer 1

A dynamo is a mechanical device for making electricity. A shaft containing separate electrical windings of copper wire, is rotated inside a magnetic field, created inside the casing, either by permanent magnets or a field winding.

Dynamos produce DC electric current.

They used to be popular in older cars, because they produce DC current, suitable for charging a battery.

They have been replaced by more efficient, AC Alternators, in modern vehicles.

These can produce more power at a wider speed range. Modern electronics allow easy conversion of the AC, to DC, for charging and electronics inside the modern car.
a type of electrical generator
Dynamo is a word that used to simply mean an electric generator, but today a dynamo refers to a generator which produces direct current (DC) using a commutator, an electrical switch that generates electricity from the force of a rotating rod. Like any other generator, the purpose of adynamo is to produce electricity from mechanical power. The source of the mechanical power could be a dam, windmill, or a coal or oil-burning power plant, with the latter being most common. Dynamos were quickly replaced by other electrical generators because of the advantages of alternating current (AC), inefficiencies of the commutator, and solid state methods for converting AC into DC power.