Cron jobs are scheduled tasks, which are executed on regular time intervals pre-set by the user and they execute scripts developed in several programming languages - PHP, Perl, Bash, and so on. In accordance with what exactly a cron needs to do, it may run each minute, every week or perhaps each year. There're plenty of useful applications to employ cron jobs in your day-to-day administration of a website. For example, a backup of the full website can be generated once per day or once per week or an email message with all fresh signups for the day can be sent to a particular email address. This kind of automatic options will make the management of every website much easier. There aren't any precise file types that can be allowed / forbidden, so every script can be run with a cron job.