Что делают операторы selective_refresh и add_partial

d postMessage support for site title and description for the Theme Customizer.
 *
 * @param WP_Customize_Manager $wp_customize Theme Customizer object.
 */
function newses_customize_register($wp_customize) {

    // Load customize controls.
    require get_template_directory().'/inc/ansar/customize/customizer-control.php';

    // Load customize sanitize.
    require get_template_directory().'/inc/ansar/customize/customizer-sanitize.php';

    $wp_customize->get_setting('blogname')->transport         = 'postMessage';
    $wp_customize->get_setting('blogdescription')->transport  = 'postMessage';
    $wp_customize->get_setting('header_textcolor')->transport = 'postMessage';

    if (isset($wp_customize->selective_refresh)) {
        $wp_customize->selective_refresh->add_partial('blogname', array(
                'selector'        => '.site-title a',
                'render_callback' => 'newses_customize_partial_blogname',
            ));
        
        $wp_customize->selective_refresh->add_partial('blogdescription', array(
                'selector'        => '.site-description',
                'render_callback' => 'newses_customize_partial_blogdescription',
            ));     

        $wp_customize->selective_refresh->add_partial('newses_header_fb_link', array(
                'selector'        => '.mg-headwidget .mg-head-detail .info-right',
                'render_callback' => 'newses_customize_partial_newses_header_fb_link',
        ));


        $wp_customize->selective_refresh->add_partial('banner_advertisement_section', array(
                'selector'        => '.header-ads',
                'render_callback' => 'newses_customize_partial_banner_advertisement_section',
        ));

        $wp_customize->selective_refresh->add_partial('select_slider_news_category', array(
                'selector'        => '.homemain',
                'render_callback' => '.newses_customize_partial_select_slider_news_category',
        ));

        $wp_customize->selective_refresh->add_partial('latest_tab_title', array(
                'selector'        => '.top-right-area .nav-tabs',
                'render_callback' => '.newses_customize_partial_latest_tab_title',
        ));


        $wp_customize->selective_refresh->add_partial('show_popular_tags_title', array(
                'selector'        => '.mg-tpt-txnlst strong',
                'render_callback' => 'newses_customize_partial_show_popular_tags_title',
        ));

        $wp_customize->selective_refresh->add_partial('newses_date_time_show_type', array(
                'selector'        => '.mg-head-detail .info-left li',
                'render_callback' => 'newses_customize_partial_newses_date_time_show_type',
        ));

        $wp_customize->selective_refresh->add_partial('flash_news_title', array(
                'selector'        => '.mg-latest-news .bn_title h2',
                'render_callback' => 'newses_customize_partial_flash_news_title',
        ));

        $wp_customize->selective_refresh->add_partial('trending_post_title', array(
                'selector'        => '.recentarea .mg-sec-title h4',
                'render_callback' => 'newses_customize_partial_trending_section_title',
        ));


        $wp_customize->selective_refresh->add_partial('you_missed_title', array(
                'selector'        => '.missed-inner .mg-sec-title h4',
                'render_callback' => 'newses_customize_partial_you_missed_title',
        ));


        $wp_customize->selective_refresh->add_partial('header_search_enable', array(
                'selector'        => '.mg-search-box',
                'render_callback' => 'newses_customize_partial_header_search_enable',
        ));

        $wp_customize->selective_refresh->add_partial('newses_footer_fb_link', array(
                'selector'        => '.mg-social',
                'render_callback' => 'newses_customize_partial_newses_footer_fb_link',
        ));

    }