jQuery .find() gets all the descendants of each element in the current set of matched elements, filtered by a selector; Also check jQuery .children() if you need to get only first level of depth;
js:
$('ul').find('li.target')
.css('background-color', 'yellow')
.append(' <span class="label label-info">.target</span>');
html:
<ul> <li>list item</li> <li>list item <ul> <li>list item</li> <li class="target">list item with target class</li> <li>list item</li> </ul> </li> <li class="target">list item with target class</li> <li>list item</li> <li>list item <ul> <li>list item</li> <li class="target">list item with target class</li> <li>list item</li> </ul> </li> <li>list item</li> <li class="target">list item with target class</li> </ul>