jQuery function $('selector', variable) [RESOLVED]

jQuery function $('selector', variable) [RESOLVED]

Hello everybody,
I'm reading a book about jQuery and sometimes it's writen something like $('selector', variable), but I only know the meaning of $('selector'), and the author doesn't explain. So what's the utility of the variable at the end of the function $() after the coma ? Why it is used ?

An exemple of code given in the book is
 $(document).ready(function() {
      $('#news-feed').each(function() {
            var $container = $(this);
            $container.empty();
            $.get('news/feed.xml', function(data) {
                  $('rss item', data).each(function() {
                        // Manipuler les nouvelles.
                  });
            });
      });
});