an article I wrote for SimpleHelp.net :
Apart from video games one of the great advantages of using computers is that they don’t seem to mind doing boring and repetitive tasks that we would rather not do. For monotonous tasks such as running daily backups we are better off scheduling them to run at a certain time every day, and do more interesting stuff with our time. Linux and UNIX usually come with the utility “crontab” by default. This very useful command allows you to schedule tasks to run at a specified time and repeat as configured. A task scheduled using “crontab” is called a “cron job”.