With Cron Jobs can automatically run a script at regular intervals, e.g. once a month once a week etc.
We wouldn't recommend using Cron Jobs unless you know what you are doing or have full detailed instructions to follow.
There are Standard and Advanced menus
in the Cron job section
Standard Cron interface
Advanced Cron interface
It is best not to execute a script you have written your self, unless you are100% sure that there is no chance of it jumping into an infinite loop and causing the server performance problems.