The document discusses extending the functionality of Plesk for Linux to integrate with external web services like the SoftLayer API. It provides an overview of Plesk modules and the SoftLayer API. As an example, it describes a SoftLayer module for Plesk that allows users to view server details, bandwidth usage, manage power/reboot, view invoices and tickets through the SoftLayer API. It explains how the module was built in PHP using the Plesk and SoftLayer APIs.