Detailed overview of 'Cron' automated tasks in Drupal 8.
Cron automated tasks
The term 'Cron' refers to the automated tasks that your site runs every N hours. It takes care of, for example, checking whether or not updates are available for Drupal core, and for your contributed modules, and themes.
By default 'Cron' runs every three hours, which can be changed to every hour, every 6-hours (or more). You can run cron anytime you like from the top of the "Reports" > "Status report" page, and contributed modules are available for additional cron functionalities.