Given this snippet of HTML and jQuery code, what does the jQuery do?

<ul class="menu">
  <li><a href="#" class="active">Home</a></li>
  <li><a href="#">Page 2</a></li>
</ul>
<ul class="active submenu">
  <li><a href="#">Subpage 1</a></li>
  <li><a href="#">Subpage 2</a></li>
</ul>

var m = $('.menu'),
  sm = $('.submenu');
m.add(sm);
m.css('font-weight', 'bold');