Is there a specific device you want to understand?
I think the only piezoelectric application i can think of is in the ignitors for cigarette lighters and those in barbecues.
The speakers in a musical card are piezoelectric, as is that "beep" in your computer.They can also be used as sensors, giving off voltages when twisted or stretched, or to generate electricity directly from mechanical effort (there has been some work on fitting piezoelectric generators into shoe-heels to charge small devices).
Wow, you just made me smarter!
My work here is done...
can i also ask the application for piezo shoe... is it efficient?:)
Google is your friend...
Certain crystalline materials have the property that when stressed, bent or struck the atoms in the crystal lattice deform this causes electrons to be ejected from the atoms - these electrons constitute an electric current. this can be large enough to make a significant spark.
I didn't even search. I just typed the following url. http://en.wikipedia.org/wiki/Piezoelectric_effectFunny how that worked.