-# To avoid that, we save a copy of the current aux file and compare it
-# to the new one afterwards. If the files are the same, great, put the
-# old one (with the old timestamp) back. If not, we need to compile
-# again, so we just invoke $(MAKE) again on this target.
+# At the start of this target, we call $(LATEX) to compile $(PN).tex.
+# If you ignore the "sed" for now, then the next step is to check for
+# the existence of a "previous" file. If there isn't one, this is the
+# first time that we've tried to build the PDF. In that case, take the
+# PDF that we've just built and make *that* the previous file. Then
+# start all over. If there is a previous file, then this is the second
+# (or more) time that we've tried to build the PDF. We diff the PDF
+# file that we've just built against the previous file; if they're the
+# same, then we've succeeded and stop. Otherwise, we make the new PDF
+# the previous file, and start all over. The end result is that we
+# will loop until the newly-created PDF and the previous file are
+# identical.