The propulsion system often consists of a combination of an engine or motor, a gearbox and wheel and axles (or caterpillar tracks) in standard applications.
The invention of the wheel allowed for the development of vehicles like Carts and Wagons that make more efficient use of muscle power, allowing larger loads to be transported.
Vehicles drawn by humans and domesticated animals are not economically as important as they once were, but they still exist.
The development of the steam engine and internal combustion engine allowed for the development of rail vehicles and motor vehicles, all of which have some form of a powertrain.
The electric motor allowed for quieter vehicles with lower emissions, and frequently higher engine efficiency.