Some of Moodle's functions happen on a regular, timed schedule. The most visible example is mailing out notices to the subscribers of a forum that a new message has been posted. A script called cron.php checks periodically to see whether new messages have been posted to any forum. If so, the script causes the notice to be emailed to the members of that forum.
The cron job also triggers routines that clean up old data and back up your courses.
The cron.php script must be triggered at regular intervals. You can set this interval. The mechanism that triggers the script is called a cron job. Directions for setting up the cron job are in the http://moodle.org/ installation guide.
Some web-hosting services allow you to set ...
