Explanation of wp_users, wp_usermeta and wp_signups

Hello,

I’m new with wordpress but I have experience with PHP and MySQL for few years. I’m trying to figure out how really wordpress works.

My question is about those three tables mentioned in topic title.

So, if I register new user, user is stored to wp_users table with user_status = 0 and sometimes empty, sometimes not user_activation_key.

Table wp_usermeta stores activation_key, and when I try to activate profile with emailed link I’m going through wp-activate.php which calls
$result = wpmu_activate_signup($key);.

If I find that function in ms-functions.php (that’s only place where I found it), it calls this query:

$signup = $wpdb->get_row( $wpdb->prepare(“SELECT * FROM $wpdb->signups WHERE activation_key = %s”, $key) );

Then I go to wp_signups and that table is empty no matter if some user is activated or not.

So, I need to know how registration and activation process really works.

Also, if I need to make new user registration (and activated user) from some other remote host, which tables do I need to updated.
I don’t have ability to include any WP file, only I can connect directly to database.

Best regards.