The first distinction of an electric motor is whether it is brushless or brushed.
Brushed motors are generally lower cost, and lower performance motors. They're most often used in intermittent industrial applications where high power density and efficiency aren't as important as cost.
Brushless motors are generally higher cost, but have the primary advantage of being essentially maintenance-free, as there are no brushes to wear out. They also offer more power density, and higher efficiency.
The basic components are magnets and copper coils. When an electric motor consumes energy, it will drive the output shaft of the motor (converting electrical energy to mechanical). If the output shaft is driven, the motor will produce energy (converting mechanical energy into electrical).
Hub Motor (Click here for more information)
Mid-Drive Motor (Click here for more information)
Bottom Bracket Drive
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