Three phase induction motors employ a simple construction made up of a stator covered with electromagnets, and a rotor composed of conductors shorted at each end, arranged as a “squirrel cage”. They work on the principle of induction in which a rotating electro-magnetic field it made by applying a three-stage current at the stators electromagnets. Therefore induces a current within the rotor’s conductors, which in turns produces rotor’s magnetic field that tries to check out stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are simple and rugged in construction. They are better quality and can operate in virtually any environmental condition
Induction motors are cheaper in expense because of simple rotor construction, lack of brushes, commutators, and slide rings
They are free of maintenance motors unlike dc motors due to the absence of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive conditions as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Devices meaning that the rotor will not turn at the precise same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to create the induction in to the rotor. The difference between your two is named the slip. Slip should be kept in a optimal range in order for the motor to operate efficiently. Roboteq AC Induction controllers could be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open loop mode in which a control causes a simultaneous, fixed-ratio Frequency and Voltage modify.
Controlled Slip: a Closed Loop speed where voltage and frequency are managed to keep slip within a narrow range while working at a preferred speed.
Field Oriented Control (Induction in Motor Vector Drive): a Closed Loop Acceleration 
and Torque control that functions by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Discover this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and function.