The cron utility allows the user to schedule programs for execution at a later time. Programs can be scheduled to run once using ths at command or at regular intervalls using the crontab command. The cron utility runs the scheduled program and mails its output back to the user.
Programs which are good examples for the use of cron are very large simulation programs, which can be run late at night, or file transfer programs, which might work better at night, when the internet is less used.
When submitting programs to cron it is important to bear in mind, that the user's shell will not be run and no paths etc. will be set up.