Where does echo output if it is written inside callback function of plugin?

Where does echo output if it is written inside callback function of register_activation_hook of plugin?

<?php
/*
 * Plugin Name:       Plugin Test 01
 * Plugin URI:        https://
 * Description:       This is a test plugin.
 * Version:           1.0.0
 * Author:            User1
 * Author URI:        https://
 * Text Domain:       plugin-test01
 */
 
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

register_activation_hook(__FILE__, 'plugin_test01_activate_plugin');

function plugin_test01_activate_plugin() {
	echo 'Hello';
}

register_deactivation_hook(__FILE__, 'plugin_test01_deactivate_plugin');

function plugin_test01_deactivate_plugin() {
	
}