Cron jobs are timetabled tasks, that run on regular intervals of time pre-set by the user and they execute scripts written in various programming languages - PHP, Perl, Bash, etcetera. In accordance with what exactly a cron needs to do, it can run every single minute, every week or even annually. There're lots of practical applications to employ cron jobs in the daily management of a site. For instance, a backup copy of the entire website can be generated once per day as well as weekly or an e-mail with all new signups for the day can be sent to a particular e-mail. This kind of automated options will make the management of every site faster and easier. There are no specific file types which are allowed or forbidden, so every script can be run using a cron job.