Create custom shortcode in WordPress

If you want to create a shortcode for including custom functionality or an HTML block in your WordPress website then you can use following teeny-weeny snippet. Then in the frontend you can use it as [shortcode_name]

add_shortcode( 'shortcode_name', 'create_custom_shortcode' );
function create_custom_shortcode( $atts ) {
ob_start();

custom functionality code goes here

return  ob_get_clean();
}