It is used to add the previous set of elements on the stack to the current set.
<!DOCTYPE html>
<html>
<head>
<style>
p, div { margin:5px; padding:5px; }
.border { border: 2px solid blue; }
.background { background:pink; }
</style>
<script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
<div>
<p>My name is Mahak Garg</p>
<p>This is C# Corner</p>
</div>
<script>
$("div").find("p").andSelf().addClass("border");
$("div").find("p").addClass("background");
</script>
</body>
</html>
Output: