Short answers, pulled from the story.
An electric motor is a machine that converts electrical energy into mechanical energy. Most operate through the interaction between the motor's magnetic field and electric current in a wire winding, producing a force in the form of torque applied to the motor's shaft.
Michael Faraday gave the first demonstration of rotary motion on the 3rd of September 1821 in the basement of the Royal Institution. A free-hanging wire dipped into a pool of mercury rotated around a permanent magnet when current passed through it.
An electric motor has two mechanical parts, the rotor, which moves, and the stator, which does not. Electrically it consists of the field magnets and the armature, which together form a magnetic circuit, separated by an air gap that lets the rotor turn.
A brushed DC motor uses a mechanical commutator and brushes to reverse current in the rotor windings, while a brushless DC motor replaces them with an external electronic switch synchronized to the rotor. Brushless DC motors are typically more than 85 percent efficient and can reach 96.5 percent, compared with 75 to 80 percent for brushed DC motors.
Mikhail Dolivo-Dobrovolsky invented the three-phase induction motor in 1889, in both cage-rotor and wound-rotor forms. He argued that Tesla's two-phase motor was impractical because of pulsations, which drove him to persist with three-phase work.
Electric motor efficiency ranges from around 15 to 20 percent for shaded-pole motors up to 98 percent for permanent magnet motors, with peak efficiency usually at 75 percent of rated load. Electric motors consume more than half of the electric energy produced in the United States.
The largest electric motors are used for marine propulsion, pipeline compression, and pumped-storage applications, with output exceeding 100 megawatts. Standardized electric motors also provide power for industrial fans, blowers, pumps, machine tools, and vehicles.