In UNIX OS we have time based scheduling, means you can configure your system to do cleaning or repairing job, when you are away.
cron is driven by a crontab, a configuration file that specifies shell commands to run periodically on a given schedule.
Fields

# +—————- minute (0 - 59)
# |  +————- hour (0 - 23)
# |  |  +———- day of month (1 - 31)
# |  |  |  +——- month (1 - 12)
# |  |  |  |  +—- day of week (0 - 6) (Sunday=0 or 7)
# |  |  |  |  |
*  *  *  *  *  command to be executed

Different domain control panel have different interface, but all does the same task.
Any shell command can be used to run on specific time with certain interval.

Sample: php /path/to/script.php