In case you didn’t know that, admin-ajax.php is the main file which processes all asynchronous requests (AJAX) in WordPress. So, it means that under this tag you can find all the tutorials related to WordPress AJAX.

Order Received (Thank you) page

How to Combine AJAX load more button with AJAX filters

Columns in WooCommerce

Comment Submission Without Page Refresh. No Plugins Used.

How to use Select2 for your Meta Boxes. Creating AJAX-based Posts Dropdown with Search.

3 Steps to Create AJAX Post Filters

Remove Posts in WordPress Dashboard with AJAX