frontend.html

// .content contains content
<div class="content"></div>

<script>
$(document).ready(function() {
    // ajax to fetch the slider data.
    $.ajax({
        type: 'POST',
        url: '<?php echo admin_url("admin-ajax.php"); ?>',
        data: { action: "front_page_slider" },
        success: function(data) {
            $('.content').html(data);
        }
    });
});
</script>

functions.php

<?php 


/**
 * Function to call the content
*/
function front_page_slider() {
	/**
 * The content we want to show
 */

$loadme = '<p>sample sentence</p>';

	echo $loadme;

	die();
}
add_action('wp_ajax_front_page_slider', 'front_page_slider' );
add_action('wp_ajax_nopriv_front_page_slider', 'front_page_slider');

?>