They're known by various names, including hog panels, stock panels, welded wire panels, etc. They come in different height/lenths and with various size/shape wire openings. You can find them at any farm/ranch store. These might be some "higher end" custom panels, but the same effect can be had with a little diy effort for a lot less money.

We bought 5'x16' with 4"x4" square openings for $45 each, cut them in half and framed them in cedar for our fence. Came out very nice.