WordPress at a glance
function is not described

wp_new_blog_notification() WP 2.1.0

Notifies the site admin that the setup is complete.

Sends an email with wp_mail to the new administrator that the site setup is complete, and provides them with a record of their login credentials.

No Hooks.

Return

Nothing (null).

Usage

wp_new_blog_notification( $blog_title, $blog_url, $user_id, $password );
$blog_title(string) (required)
Site title.
$blog_url(string) (required)
Site url.
$user_id(int) (required)
User ID.
$password(string) (required)
User's Password.

Code of wp new blog notification: wp-admin/includes/upgrade.php VER 5.1.1

<?php
function wp_new_blog_notification( $blog_title, $blog_url, $user_id, $password ) {
	$user      = new WP_User( $user_id );
	$email     = $user->user_email;
	$name      = $user->user_login;
	$login_url = wp_login_url();
	/* translators: New site notification email. 1: New site URL, 2: User login, 3: User password or password reset link, 4: Login URL */
	$message = sprintf(
		__(
			'Your new WordPress site has been successfully set up at:

%1$s

You can log in to the administrator account with the following information:

Username: %2$s
Password: %3$s
Log in here: %4$s

We hope you enjoy your new site. Thanks!

--The WordPress Team
https://wordpress.org/
'
		),
		$blog_url,
		$name,
		$password,
		$login_url
	);

	@wp_mail( $email, __( 'New WordPress Site' ), $message );
}