It is the same piece of meat that is used for pork chops. However this does not have the bones on it. Take the thin connective tissue off the top of the meat with a thin knife with a good point on it.
This is called a butterfly cut. You cut down almost all the way but not all the way.
Then you cut another thin cut only all the way this time.
You then have a large very thin cutlet.
Here I cover the pork cutlet (schnitzel) with a plastic storage bag both underneath it as well as on top. the gallon size works perfect. Plastic wrap works well also but you have to be careful not to rip it when you pound it.
Pound the cutlet to make it thin. If you don't have a meat mallet, you can use the back of a knife or a the side of a plate. Wooden mallets are very inexpensive and worth the small investment.