A cron job is an automated task, which performs a certain action - usually executing some script in a website hosting account. The task is planned, so it will run regularly - weekly, daily, hourly etc. There are many reasons to employ a cron job for your sites. As an example, you can get regular reports how many site visitors have signed up on your website, some temp folder can be emptied automatically weekly or a backup copy of your content can be created in a separate folder in your hosting account. Using cron jobs will help you with the management of your websites because you are able to get many things carried out automatically and have reports for them, instead of spending time and efforts to complete them by hand.