How to display featured image description and title?

this might work:

$post_thumbnail_id = get_post_thumbnail_id($post->ID);
$thumbnail_image = get_posts(array('p' => $post_thumbnail_id, 'post_type' => 'attachment'));
if ($thumbnail_image && isset($thumbnail_image[0])) {
$img_description = $thumbnail_image[0]->post_content;
$img_caption = $thumbnail_image[0]->post_excerpt;
$img_alt = get_post_meta($post_thumbnail_id , '_wp_attachment_image_alt', true);
$img_title = $thumbnail_image[0]->post_title;
}