WordPress at a glance
function is not described

render_block_core_block() WP 1.0

Renders the core/block block on server.

No Hooks.

Return

String. Rendered HTML of the referenced block.

Usage

render_block_core_block( $attributes );
$attributes(array) (required)
The block attributes.

Code of render block core block: wp-includes/blocks/block.php WP 5.2.2

<?php
function render_block_core_block( $attributes ) {
	if ( empty( $attributes['ref'] ) ) {
		return '';
	}

	$reusable_block = get_post( $attributes['ref'] );
	if ( ! $reusable_block || 'wp_block' !== $reusable_block->post_type ) {
		return '';
	}

	if ( 'publish' !== $reusable_block->post_status || ! empty( $reusable_block->post_password ) ) {
		return '';
	}

	return do_blocks( $reusable_block->post_content );
}