The cron service allows arbitrary command-line tasks to be scheduled at various intervals: hourly, daily, weekly or monthly, with a granularity down to one minute. Tasks are specified by means of the crontab, which is stored on a per-user basis for execution by the cron daemon.
Depending on the setup, you might have to be in the cron group to create a crontab.
Scheduling jobs on computers which don't run permanently (home computers, computers in offices etc.) can use fcron either additionally to cron or even as exclusive scheduler.