That's what this does right here:
$("#output").append($(this).attr("name") + "<br />");
That is saying: Append to (add to the end of) the html element that has an id of "output". The text to add is the value in the "name" attribute of the current object (THIS object) I am looping through, and the loop is iterating through every "var" tag in the $(xml) object.
Make sure you have an element in your html (a div tag for example) with an id of "output". Without it, nothing happens. You can actually create it using jQuery:
But it's easy enough just to put it in your html.