WordPress at a glance
function is not described

add_user() WP 2.0.0

Creates a new user from the "Users" form using $_POST information.

No Hooks.

Return

Int/WP_Error. WP_Error or User ID.

Usage

add_user();

Code of add user: wp-admin/includes/user.php VER 5.1.1

<?php
function add_user() {
	return edit_user();
}