alert($(this).attr('id'))
<p id="test" class="hello">Hello</p>
<script>
//Hide all html elements "p"
$("p").hide();
//Hide id="Test"
$("#test").hide();
//Hide all class="hello"
$(".hello").hide();
//Hide all "p" with class="hello"
$("p.test").hide();
</script>
$( "#myDiv" )