Stator is the outer shell of the generator which is stationary and holds either the field producing coils or the permanent magnets according to the type of the field excitation. This is the way which the main magnetic field is produced. This can be achieved by using permanent magnets or using electromagnets. The electromagnets are sets of coils put around the stator. These coils compensate for the drop in voltage.
Brushes are the one of the most important parts of a generator.
In a DC generator brushes make contact with the commutator and they are connected to an outer circuit. So they work as a bridge between the generator and the outer circuit . Brushes work in pairs across each other. When a pair of conducting bars of the commutator come in contact the induced current produced passes to the outer circuit. This way , when the conducting bars come in contact with the brushes simultaneously, a pulsing current is produced.