What is a cron job?
Posted by drupallovers on February 28, 2012
Many Drupal modules have tasks that have to take place from time to time. Think of cron as the tolling of a bell, letting Drupal know that it should perform the appropriate tasks.
The actual “cron job” is a time-triggered action that is usually (and most efficiently) performed by your website’s hosting server, but can also be configured by a remote service or even from your own desktop.
For your Drupal site, what actually happens is that the cron job triggers an invisible visit to the site’s cron.php file (http://www.example.com/cron.php) which, in turn, executes tasks on behalf of installed modules.
Triggering Drupal cron without a cron job
With the inclusion of “Poor man’s cron” in the Drupal 7 core, it is no longer necessary to set up a cron job on your web server. Instead, you can configure the frequency with which cron is run on admin/config/system/cron (Administration > Configuration > System > Cron).
In Drupal 6, you can do the same thing by installing the contributed Poormanscron module.