Active PFC or Passive PFC?

can anyone tell what is it? is there any difference of it?
tried read it from wiki, not so sure about it

was looking for a psu for a friend for previous setup
e7200, one hdd, hd3650, p43 mobo.

good enough? would be there any problem in future?
Newegg.com - Thermaltake W0093RU 500W ATX 12V 2.0 Version Passive PFC Power Supply - Power Supplies

 

I believe it reduces the amount of power that can't/isn't used so you save power.. Not sure though.

 

PFC and Efficiency are different.

 

yeah, just read the article
then the psu above won't be any problem right?

 

as usual, budget constraint

he only willing to fork out $30
unless I can give him some crucial reason why he should get the corsair

 

so
Newegg.com - Thermaltake W0093RU 500W ATX 12V 2.0 Version Passive PFC Power Supply - Power Supplies

good to go?

 

I see, then off to find other

 

How about this one:
Newegg.com - OCZ StealthXStream OCZ500SXS 500W ATX12V / EPS12V Active PFC Power Supply - Power Supplies

 

IINM, I read somewhere that having PFC means your voltage is automatically controlled, no need that red switch anymore.

And Active PFC tend to be good on the electric consumption, but only from the power supplier point of view