A device that plugs in between the wall socket and your computer's power supply. It smoothes out the flow of electricity to your computer, filtering out surges, spikes and brownouts.
A device that is in-between a surge suppressor and a UPS. Typically, Power Conditoners use very small batteries or very large capacitors or both to fill in (or bridge the lack of correct voltage) and bring an undervoltage up to spec for a very short time.
A unit which processes AC electrical power (typically 120V) to maintain constant voltage, supress spikes, moderate brown-outs, and filter out un-wanted noise.