I was quite shocked 
when a fellow camper I was chatting to didn’t know what CMS meant.
If you are a web developer you should know this.
This tutorial is free until tomorrow but if you reach this after 30 Oct, please Google “CMS”.
https://www.linkedin.com/learning/joomla-3-essential-training/understanding-joomla
Examples of CMS’s are WordPress, joomla, Drupal, etc. There are now hundreds out there.