Regenerators like PS Audio and the like are both. As they output a steady 120volts.(and some one can adjust the voltage to what one wants to some degree. The PS Audio P600 and family with the optional board can also adjust the frequency of the A/C current, to interesting effect)
Some Furman power conditioners have a 'power factor' device to alleviate drops in voltage by using a 'stiffening cap' (sort of like the automotive audio type)
Generally unless you have widely fluctuating voltage, you do not need a voltage regulator.
Normal voltage ranges of 115 to 125 volts are no big deal.
Once you are getting sags down to 110V or overvoltage of 130 volts Then you have a problem
And I am certain the heading has the correct question. The body of the op's text is just a mistake, and he does mean power conditioner and voltage regulator.