Most turntables use an a/c synchronous motor, ie it locks to the frequency of the mains, not the voltage. Such motors are accurate, reliable and cheap, if you choose well, they are virtually silent and vibration free.
To change the speed of the turntable platter, you either change the speed of the motor, which is complicated as you have to change the frequency of the a/c that drives the motor.
Or, you change the size of the spindel, which in effect alters the 'gearing', ie the relationship between the spindle and the platter/sub platter assembly. This can be done by switching a guide between the two different diameters on a stepped pulley, easy enough but it will compromise the condition of the belt.
Or you can swith the belt by hand which is easier on the belt, in some designs, early LP12s for example, an oversize collar is fitted onto the single diameter spindel, all of course done by hand.
Then the marketing guys get to work to make sure that you 'understand' that their choice is for the best possible SQ.