Cron is something which is executed at a certain interval of times to do some sort of task! Such as delete temporary files after some period of time

<span style="color: rgb(51, 51, 51); font-family: &quot;Lucida Grande&quot;, &quot;Lucida Sans Unicode&quot;, &quot;DejaVu Sans&quot;, &quot;Lucida Sans&quot;, sans-serif; font-size: 13.008px; line-height: 20.0063px;">Cron takes care of running periodic tasks like checking for updates and indexing content for search.</span>

Cron is a feature in Drupal which helps to schedule the periodic jobs, for example, if a notification has to be sent of of Drupal Application every hour, then this can be done using Cron. This tutorial helps explains Cron in detail - https://docs.acquia.com/cloud/manage/cron