WordPress at a glance
function is not described

install_network() WP 3.0.0

Install Network.

No Hooks.

Return

Nothing (null).

Usage

install_network();

Code of install network: wp-admin/includes/schema.php VER 5.0.3

<?php
function install_network() {
	if ( ! defined( 'WP_INSTALLING_NETWORK' ) )
		define( 'WP_INSTALLING_NETWORK', true );

	dbDelta( wp_get_db_schema( 'global' ) );
}