On many different pieces of machinery or vehicles, there is a generator. The object that turns the generator is called the prime mover. There also may be an alternator. A generator takes the mechanical energy from turning or something and then converts it into the electricity that is needed to make the machine function. The alternator may be used to use a different or alternate electrical current.
Sometimes, the generator and alternator are used to describe the same part on the machine. These words may be used interchangeably. Sometimes, the alternator or generator shuts down while the vehicle is still in motion. If the prime mover of an alternator in which it is supplying a load does shut down, it will continue to run as a synchronous motor in the same direction.