Three phase induction motors have a very simple construction made up of a Induction Motor stator covered with electromagnets, and a rotor made up of conductors shorted at each end, arranged as a “squirrel cage”. They work on the basic principle of induction where a rotating electro-magnetic field it produced through the use of a three-phase current at the stators electromagnets. Therefore induces a current in the rotor’s conductors, which in turns creates rotor’s magnetic field that attempts to check out stator’s magnetic field, pulling the rotor into rotation.
Great things about AC Induction Motors are:
Induction motors are simple and rugged in building. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost because of simple rotor construction, lack of brushes, commutators, and slide rings
They are free of maintenance motors unlike dc motors due to the lack of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive environments as they don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Machines and therefore the rotor will not turn at the exact same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator quickness is necessary to be able to produce the induction in to the rotor. The difference between the two is named the slip. Slip should be kept in a optimal range to ensure that the motor to use effectively. Roboteq AC Induction controllers can be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open up loop mode in which a command causes a simultaneous, fixed-ratio Frequency and Voltage change.
Controlled Slip: a Closed Loop speed where voltage and frequency are managed in order to keep slip within a narrow range while operating at a preferred speed.
Field Oriented Control (Vector Drive): a Closed Loop Swiftness and Torque control that functions by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Observe this 
video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and function.