Electrical machines are classified into two..
Motor.
Generator.
There are two types of motor.
AC motor.
DC motor.
There are two kinds of three phase motor.
Synchronous motor.
Asynchronous motor.
The basic difference between asynchronous and synchronous motor , slip presents in asynchronous engine .At running condition slip of an asynchronous electric motor lies from 0 to 1 1. . In asynchronous engine both starting 
and working torque is required. Asynchronous motor has moderate beginning torque . Asynchronous motor can be a single fed electric motor.In asynchronous electric motor field is stationary armature rotates .
Three phase synchronous machines have got a stationary three phase armature and a wound rotor. They are of two types:
synchronous generator or Alternator: Primary workhorse of the energy generation industry; they are rotated mechanically by a prime mover at synchronous acceleration and it generates three phase electricity. Image of PMA used in cars:
2. Synchronous motor: They are continuous speed three phase devices capable of operating at synchronous speed. They are mostly used in constant velocity mechanical drives. They are better in comparison to induction motors.
A synchronous machine has derived its name from the idea that the rotor will rotate in 12v Motor synchronicity with the rotating magnetic field.
Simply speaking, for a 2 Pole machine (electric motor) the rotating magnetic field rotates at 3000 rpm; the rotor of synchronous machine also rotates at the same acceleration i.electronic. 3000 rpm. That is achieved through special constructional features in production this types of devices. There is absolutely no slip in synchronous machines like regular induction motors.
Normally three phase supply is available commercially and the design is also meant for the same. This is why ‘three phase’ is definitely added with synchronous machine name.