What is the difference between the "complete" and " checkout complete" order statuses?

Question

I am using the Drupal 7 Commerce module. I would like to execute a special code when the payment of the order is completed.

What is the difference between checkout complete and complete?

I googled and I found suggestions for these hook implementations.

First option

function mymodule_commerce_order_update($order) {
  if ($order->status == 'completed' ) {
    // ...
  }
}

Second option

function my_module_commerce_order_presave($order) {
  if ($order->status == 'completed' ) {
    // ...
  }
}

###Third option

I found some suggestions to implement hook_commerce_order_updated().

Fourth option

function mymodule_commerce_checkout_complete($order) {
  if ($order->status == 'completed' ) {
    // ...
  }
}

Answer 1

None of the above. You should be using hook_commerce_payment_order_paid_in_full(), which is always invoked the first time an order's balance drops to $0 or less.

Read more about it in commerce/modules/payment/commerce_payment.api.php.