WordPress at a glance
function is not described

post_custom_meta_box() WP 2.6.0

Display custom fields form fields.

No Hooks.

Return

Nothing (null).

Usage

post_custom_meta_box( $post );
$post(object) (required)

Code of post custom meta box: wp-admin/includes/meta-boxes.php VER 5.0.3

<?php
function post_custom_meta_box($post) {
?>
<div id="postcustomstuff">
<div id="ajax-response"></div>
<?php
$metadata = has_meta($post->ID);
foreach ( $metadata as $key => $value ) {
	if ( is_protected_meta( $metadata[ $key ][ 'meta_key' ], 'post' ) || ! current_user_can( 'edit_post_meta', $post->ID, $metadata[ $key ][ 'meta_key' ] ) )
		unset( $metadata[ $key ] );
}
list_meta( $metadata );
meta_form( $post ); ?>
</div>
<p><?php
	printf(
		/* translators: %s: Codex URL */
		__( 'Custom fields can be used to add extra metadata to a post that you can <a href="%s">use in your theme</a>.' ),
		__( 'https://codex.wordpress.org/Using_Custom_Fields' )
	);
?></p>
<?php
}