How to create shortcode of template in WordPress code example

Example 1: wordpress create shortcode

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

Example 2: wordpress create shortcode

// function that runs when shortcode is called
function wpb_demo_shortcode() { 
 
// Things that you want to do. 
$message = 'Hello world!'; 
 
// Output needs to be return
return $message;
} 
// register shortcode
add_shortcode('greeting', 'wpb_demo_shortcode');