An induction motor or 3 phase induction motor is an AC electric electric motor in which the electric current in the rotor had a need to generate torque is obtained by electroThree Phase Motor magnetic induction from the magnetic field of the stator winding
An induction electric motor which connects with a 3-stage supply called 3-phase induction motor. Example followers,blowers, cranes,traction .It really is a ac electric motor. The primary drawback of DC motors is the presence of commutator and brushes, which require regular maintenance and we can not use DC motor in explosive and filthy environment. But induction motors are cheaper,rugged,lighter,smaller,require much less maintenance and will use in dirty and explosive environment. Slide s may be the imp element in this kind of motor.
There are 2 types of IM.
Squirrel cage IM
Slip ring IM
There are various starting and braking condition.
Important starting 
methods are
Star-delta starter
Auto transformer starter
Ac voltage controller starter
Rotor resistance starter
Important braking methods are
Regenerative braking
Plugging or reverse voltage braking
Dynamic braking
But one thing velocity control technique of induction electric motor is important
Pole changing
Stator voltage control
V/f control
Slip power recovery
Rotor resistance control