What The Differences Between Dc Motor And Dc Generator?

The motor uses the supplied current to excite the fields which cause rotation and a shaft is powered to turn and do work.
In the generator, external mechanical force (such as the drive belt on a car turning the pulley on the alternator) is applied to turn the shaft which excites the fields and allows current to be drawn off and provides power for work.
One uses elect. Power to provide force, while the other uses force to produce elect. Power.