Electrical machines are classified into two..
Motor.
Generator.
There are two kinds 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 electric motor , slip presents in asynchronous electric motor .At running condition slide of an asynchronous motor lies from 0 to 1 1. . In asynchronous engine both starting and running torque is necessary. Asynchronous motor has moderate beginning torque . Asynchronous motor is definitely a single fed motor.In asynchronous 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: Main workhorse of the power generation industry; they are rotated mechanically by a primary mover at synchronous swiftness and it generates three phase electricity. Image of PMA used in cars:
2. Synchronous motor: They are constant speed three phase devices capable of working at synchronous rate. They are mostly used in constant rate 12v Motor mechanical drives. They are more efficient compared to induction motors.
A synchronous machine has derived its name from the idea that the 
rotor will rotate in 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 rate i.e. 3000 rpm. That is achieved through unique constructional features in manufacturing this types of machines. There is absolutely no slip in synchronous devices like regular induction motors.
Normally three phase supply is available commercially and the look is also meant for the same. This is why ‘three phase’ is certainly added with synchronous machine name.