The CRON module is designed as a mechanism to run regular maintenance and functions via a single entry point. The process works by calling the "cron.php" file. This in turn does the following

• Checks all active modules for a pncron.php file. If it exists, include it.
• Checks for a module_cron() and if it exists, run it.
• Scroll through the zk_cron table and run all registered functions.

The zk_cron table allows users to register functions (and parameters) to be called by the cron process.