Although I’ve been dealing with webshoting and webdesign since 1995, it took me a whilw to figure this one out. If you’re used to shared shosting packages, it’s likely that you’ve never come in contact with this. Hence, this article is aimed at people who don’t know what it is.
As explained in Wikipedia:
Cron is the name of a program that enables unix users to execute commands or scripts (groups of commands) automatically at a specified time/date. It is normally used for sys admin commands, like makewhatis, which builds a search database for the man -k command, or for running a backup script, but can be used for anything. A common use for it today is connecting to the internet and downloading your email.
So a cronjob is a scheduled action, which is executed by and on your web server. WordPress itself doesn’t do this for you. It’s like having a monkey sitting at a command prompt, typing something in every minute/hour/day – in regular intervals – you get the drift.
In order to setup this automatic execution, you need to be in control of your own dedicated or virtual server. If you’re on shared a shared hosting plain, you can ask your provider to setup a cron job for you. Just tell them “I want (this particular file in this particular directory) executed every Thursday evening at 9”. Otherwise, use your own administrative panel (like Plesk or Webmin) to set this up.
Want to know how? Read the following article: How to setup a Cron Job?