Cron jobs allow you to automate certain commands or scripts on your site. You can set a command or script to run at a specific time every day, week, etc. For example, you could set a cron job to delete temporary files every week to free up disk space.
Notice: You need to have a good knowledge of Linux commands before you can use cron jobs effectively. Check your script with your hosting administrator before adding a cron job.
How to use Cron Jobs?
Click Cron Jobs icon at Advnaced Tab, see this picture
Cron Email meaning You can have cron send an email everytime it runs a command. If you do not want an email to be sent for an individual cron job you can redirect the command's output to /dev/null like this: mycommand >/dev/null 2>&1
Put your email address and click Update Email at sample above
To add New Cron Job, use this feature setting as this picture