Conditioners specifically work to smooth the sinusoidal A.C. wave form and maintain a constant voltage over varying loads.
Usually this is used for home or office applications and commonly provides surge protection as well as noise filtering.
The surge protector stops the flow of electricity from reaching a machine by shutting off the power source.
For example, if the application will be a home theater system, the noise suppression rating listed in the technical specifications of the power conditioner will be very important.
Units may be small enough to mount on a printed circuit board or large enough to protect an entire factory.
Ideally electric power would be supplied as a sine wave with the amplitude and frequency given by national standards (in the case of mains) or system specifications (in the case of a power feed not directly attached to the mains) with an impedance of zero ohms at all frequencies.