Three phase induction motors have a very simple construction composed of a 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 in which a rotating electro-magnetic field it produced by applying a three-stage current at the stators electromagnets. This in turn Induction in Motor induces a current inside the rotor’s conductors, which in turns generates rotor’s magnetic field that attempts to follow stator’s magnetic field, pulling the rotor into rotation.
Benefits of AC Induction Motors are:
Induction motors are simple and rugged in structure. They 
are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, absence of brushes, commutators, and slip rings
They are maintenance free 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 do not have brushes that may cause sparks
AC Induction motors are Asynchronous Devices and therefore the rotor does not convert at the specific same speed since the stator’s rotating magnetic field. Some difference in the rotor and stator speed is necessary in order to generate the induction in to the rotor. The difference between your two is called the slip. Slip must be kept within an optimal range to ensure that the motor to operate efficiently. Roboteq AC Induction controllers could be configured to operate in one 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 Shut Loop speed where voltage and frequency are managed to keep slip within a narrow range while running at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Speed and Torque control that works 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 about how AC Induction Motors are constructed and function.