Cron is a daemon that runs in the background and checks on a regular basis if there is anything to do. It does that by looking into each user's crontab.
For our backup script we only have to do three things:

• Download this script (SimpleBackup.php), unpack it and move it where you want. Edit it to your needs.
• Or, even better, if you have followed the howto take your new script and call it SimpleDownload.php
• Make sure the script is executable (chmod -a+rx /path/to/SimpleBackup.php)
• Add an entry in your crontab