jQueryのon()とclick()の違い

<p>
    <h1>Click</h1>
    <button class="add">Click me to add new item</button>
    <ul class="li">
        <li>I am old item.<button class="delete">Delete</button></li>
        <li>I am old item.<button class="delete">Delete</button></li>
        <li>I am old item.<button class="delete">Delete</button></li>
    </ul>
</p>

<script type="text/javascript" src="jquery-1.8.3.min.js"></script>
<script type="text/javascript">
$(".add").click(function(){
    $(".li").append(&#39;<li>I am new item.<button class="delete">Delete</button></li>&#39;);
});
$(".delete").click(function(){
    $(this).parent().remove();
});
</script>