The design of the belt drive turntable allows the use of a less expensive motor than the direct-drive turntable. Also, the elastomeric belt absorbs motor vibrations which would otherwise be picked up by the stylus.
Turntables themselves are relatively simple machines - little more than spinning wheels powered by electric motors using a thin rubber belt looped over the motor and the central axle of the turntable (known as belt drive) - In a belt drive turntable the motor is located under and to the side of the platter and is connected to the platter by an elastomeric belt. Powering the turntable at exactly the right speed is absolutely critical for playing the music correctly. If the turntable spins too slowly, the music slows down too much and lady singers end up sounding like men!
A record player is an analog device: the music is stored as bumps on the vinyl record, with the size of the bumps directly corresponding to the musical notes they store. Introduce some extra bumps (by scratching your vinyl record) and you'll find some added "music" when you play back the vinyl record - scratchy and crackly noises you really don't want to hear.