wp_enqueue_scripts, wp_register_scripts, wp_print_scripts: i’m confused

I’ve been reading up a bit on this subject, but the more I read – the more confused I get.

Can someone explain to me in short what’s the exact difference between wp_enqueue_scripts, wp_register_scripts and wp_print_scripts?

For example, I have the following code in my functions.php – and it’s working, but I do not understand why I can not use wp_print_scripts for the stylesheets, whereas the code still works if I use wp_enqueue_scripts for the javascript files:

add_action('wp_print_scripts', 'add_my_js');
function add_my_js(){
    if(!is_admin()){
        wp_enqueue_script('default',  get_bloginfo('stylesheet_directory').'/js/default.js', array('jquery'));
    }
}

add_action('wp_enqueue_scripts', 'add_my_stylesheet');
function add_my_stylesheet() {
    wp_register_style('default', get_bloginfo( 'stylesheet_url'));
    wp_enqueue_style( 'default');
}