Need some explaination about wp-includes/plugin.php/ do_action function

In login.php i got=>

do_action( 'login_enqueue_scripts' );
do_action( 'login_head' );

From wp-includes/plugin.php i get the definition of do_action function.

[Code moderated as per the Forum Rules. Do not re-insert it but use the pastebin]

What does this do function do ? So far what i can understand it call some function getting from parameter. Am i right ?

Then what do these line do ?

do_action( 'login_enqueue_scripts' );
do_action( 'login_head' );

What are ‘login_enqueue_scripts’ and ‘login_head’ ?

Doing print_r($wp_filter[$tag][‘function’] i get this result=>

https://pastebin.com/U2gWZLKd