You are welcome, and thanks for being so understanding and grateful.
I have never seen the term "filter output" on a small generator, so a more specific or detailed example might help. Is this from a nameplate, the manual, or advertising material? Is it a poorly translated reference on a generator made in China?
A generator, particularly one like the Honda 2000i which contains a built in inverter to make the output independent of motor speed might provide a "filtered output" so that pulse and RF noise from the inverter does not get into the 120 volt wiring. But not a "filter output".