In Drupal, cron performs following set of tasks :
- Checking for updates
- Indexing content for search
- Checks for available updates (If update manager is enabled) and so on.
We can schedule the cron by navigating to this url (/admin/config/system/cron) and it can be scheduled like 1hour, 3 hours, 6 hours , 12 hours, 1 day, 1 week.
We can improve the performance of the cron by disabling cron in Drupal site and setting up the cron in server side.