Some need other Applications altogether. To You, don't use it. However, let's assume you don't know anything about AppleScript, but Are Willing To Try. If you select this script, Things Happen. You leave Tex-Edit.
Windows start moving and opening.
Finally, a file is hilited. It's the file of the frontmost window of Tex-Edit Plus. The script did what the Description said it would do. And you found out where the frontmost window-document resides. You probably knew already, but you didn't have to look.