Three phase induction motors have a very simple construction made up of a stator protected with electromagnets, and a rotor composed 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 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 basic and rugged in structure. They are more robust and can operate in virtually any environmental condition
Induction motors are cheaper in expense due to 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 make the induction into the rotor. The difference between the two is named the slip. Slip must be kept within an optimal range in order for 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 controlled in order to keep slip within a narrow range while operating at a preferred speed.
Field Oriented Control (Induction Motor china Vector Drive): a Closed Loop Quickness 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.