An induction motor or asynchronous motor is an AC electric engine in which the electric current in the rotor needed to generate torque is obtained by electromagnetic induction from the magnetic field of the stator winding. … An induction motor’s rotor can be either wound type or squirrel-cage type.
Great things about AC Induction Motors are:
Induction motors are simple and ac motor rugged in structure. They are better quality and can operate in virtually 
Induction motors are cheaper in expense because of simple rotor construction, absence of brushes, commutators, and slip rings
They are maintenance free motors unlike dc motors due to the absence of brushes, commutators and slip rings
Induction motors could be operated in polluted and explosive conditions as they don’t have brushes which can cause sparks
AC Induction motors are Asynchronous Machines meaning that the rotor will not switch at the exact same speed because 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 in order for the motor to operate effectively. 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 alter.
Controlled Slip: a Closed Loop speed where voltage and frequency are controlled to keep slip within a narrow range while working at a preferred speed.
Field Oriented Control (Vector Drive): a Closed Loop Velocity and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Find this video from Learning Engineering for a visual illustration on how AC Induction Motors are constructed and work.