What are Cron Jobs?
A cron job is a Linux command that allows you to periodically execute a script or command of your site. This type of tasks are used for the periodic execution of scripts related to e-mail notifications, databases or routinely data checks.
For example, you can create a cron job to periodically execute a script that checks the temperature of a weather station located at your rooftop, thanks to this you'll be able to know the temperature of outside of your home and eventually show it at your website. While creating the cron job you can set the frequency (time interval) of this task, allowing you to indicate it to execute every minute, multiple times a day or only some days a month or year.