how to create shortcode for page in wordpress code example

Example 1: wordpress do shortcode

<?php echo do_shortcode('[name_of_shortcode parameters=""]'); ?>

Example 2: wordpress create shortcode

function create_shortcode(){
    return "<h2>Hello world !</h2>";
}
add_shortcode('my_shortcode', 'create_shortcode');
// Use [my_shortcode]