WordPress at a glance
action is not described

transition_post_status action-hook . WP 2.3.0

Fires when a post is transitioned from one status to another.

Usage

add_action( 'transition_post_status', 'action_function_name_7225', 10, 3 );
function action_function_name_7225( $new_status, $old_status, $post ){
	// action...
}
$new_status(string)
New post status.
$old_status(string)
Old post status.
$post(WP_Post)
Post object.

Where the hook is called

wp_transition_post_status()
wp-includes/post.php 4202
do_action( 'transition_post_status', $new_status, $old_status, $post );

Where the hook is used (in WP core)

wp-includes/ms-default-filters.php 56
add_action( 'transition_post_status', '_update_blog_date_on_post_publish', 10, 3 );
wp-includes/ms-default-filters.php 57
add_action( 'transition_post_status', '_update_posts_count_on_transition_post_status', 10, 3 );
wp-includes/default-filters.php 341
add_action( 'transition_post_status', '_transition_post_status', 5, 3 );
wp-includes/default-filters.php 342
add_action( 'transition_post_status', '_update_term_count_on_transition_post_status', 10, 3 );
wp-includes/default-filters.php 367
add_action( 'transition_post_status', '_wp_auto_add_pages_to_menu', 10, 3 );
wp-includes/default-filters.php 445
add_action( 'transition_post_status', '_wp_customize_publish_changeset', 10, 3 );
wp-includes/default-filters.php 448
add_action( 'transition_post_status', '_wp_keep_alive_customize_changeset_dependent_auto_drafts', 20, 3 );
wp-includes/default-filters.php 457
add_action( 'transition_post_status', '__clear_multi_author_cache' );