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New wrinkle in my brain. I never knew the was such a thing ac an AC/AC wall wart transformer. Can some enlighten my the particulars. It is my understanding if I use an AC/DC transformer on AC/AC device I will fry the circuit board. Is this true and why? Why does any circuit care as long as the voltage requirement is same?

Some components are not symetric. Take a LED, as example. In forward mode, once the voltage is high enough, typically around 1.6 volt for a red LED, the LED brights up. But if you reverse the voltage, even if the LED is a diode and could block some current, that is true only for a very, very low voltage, even as low as 0.5 volt for some LED. Using an AC voltage (alternative Current voltage source, don't shoot me, I am not the one who came with that way of naming the thing), you do exactly that: you reverse the voltage and destroy the poor LED, even if the reverse voltage, 0.5 volt, is much lower than the minimal forward voltage required to light up the LED, 1.6 volt. And a LED is not the only electronical component with that kind of behavior. Gate, OpAmp, MCU, ... the list is really long.

AC/AC would be a simple transformer which would probably give a different AC voltage from what went in. Example: 120vac in and 12vac out. It would be used to feed ac devices such as a transformer or an ac motor. AC/DC would lower the voltage and convert it to dc (a couple of different technologies could be used). Example: 120vac in and 12vdc out. It could be used for Mr. vandergast's LED with appropriate resistor or to run a dc motor. It would quickly burn out a transformer.