Garebear, as you can see, your question's not so dumb.
Bill_k says it best; power conditioner seems to be a blanket term which includes active and passive units. The active unit is a regenerator cleaning the AC line voltage by converting it to a DC sinewave and then outputting clean AC to the components. Passive uses capacitors and other proprietary electronics to remove dirty line noise and lower the noise floor.
In the Classifieds, the "AC Conditioners" listed are active and passive units, but are largely active units(regenerators).
There may be differences among some manufacturers using these terms
Bill_k says it best; power conditioner seems to be a blanket term which includes active and passive units. The active unit is a regenerator cleaning the AC line voltage by converting it to a DC sinewave and then outputting clean AC to the components. Passive uses capacitors and other proprietary electronics to remove dirty line noise and lower the noise floor.
In the Classifieds, the "AC Conditioners" listed are active and passive units, but are largely active units(regenerators).