Cron jobs are scheduled tasks, which are executed on regular intervals of time pre-set by the end user and they execute scripts coded in various programming languages - PHP, Perl, Bash, and so on. In accordance with what exactly a cron needs to do, it may run each minute, weekly or maybe once per year. There're lots of useful applications to make use of cron jobs in the daily administration of a site. For instance, a backup copy of the entire website can be generated every day as well as once a week or an email with all fresh signups for the day may be sent to a given e-mail. These types of automated options can make the administration of every website much easier. There are no specific file types that can be allowed / forbidden, so any script can be run using a cron job.