Implementing callback function in hook_menu()

Question

In the link given below , https://drupal.org/node/224333
So as given in below statement you do not have to declare the callback path* what does this mean? I have hook_menu() in d6 which is as follows :

$items['ort/add/ion'] = array(
    'type' => MENU_CALLBACK,
    'page callback' => 'ort_add_ion',
    'access arguments' => array('access content'),
    'file' => 'ort.tion.inc',
  );

Does the link say that for d7 you do not need page callback or something different?

In Drupal 7, you do not have to declare the callback path in hook_menu(), and the callback function is far simpler.

Drupal 6:

<?php
// This function must be pointed to in hook_menu() in D6.
function my_callback_function() {
  // ... Much work to build the form ....

  drupal_process_form($form_id, $form, $form_state);
  $form = drupal_rebuild_form($form_id, $form_state, $args, $form_build_id);

  $output = drupal_render($form);

  // Final rendering callback.
  print drupal_json(array('status' => TRUE, 'data' => $output));
  exit();
}
?>

Drupal 7:

<?php
// No path needs be set up to point to the function, and $form and $form_state are provided.
function my_callback_function($form, &$form_state) {
  // Often you would select a portion of the form to match #ajax['wrapper']
  // rather than processing the whole form.
  return $form;  // Either HTML or a render array may be returned.
}
?>

Answer 1

The simple answer is it is for ajax items. In drupal 6 you had to declare a path and direct your ahah to it with ['#ahah']['path']. In drupal 7 it is handled automatically and you now use ['#ajax']['callback'] to call the function without having to declare a path.