jQuery/AJAX - Load content into a div when button clicked?

Use jQuery.click and jQuery.load:

$(document).ready(function(){
    $('.classloader.').click(function(){
        $('#contenthere').load('/includes/about-info.html');
    });
})

Load latest version of jQuery:

<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>

jQuery code:

<script language="javascript">
$(function(){
  $(".classloader").click(function(){
    $("#contenthere").load("/includes/about-info.html");
  });
});
</script>

HTML code:

<p class="classloader">Click Here</p>
<div id="contenthere"></div>