Content Management System
Also often referred to (unhelpfully) as a Database Driven Website. A CMS is an application or application framework that provides the glue between a database system, a visual website design, and the functionality that makes the website actually work. Many CMS systems are designed around the MVC architecture, but some notable ones are not (WordPress for example).
Historically, websites were actually managed by people who had to understand how databases work, how to write HTML, and be able to understand at least one programming language. The requirement became clear for non-technical staff to be able to manage websites on a daily basis.
By providing a simplified and task oriented user interface, a CMS system does all of the heavy lifting, relieving website owners of the need for specialist technical expertise.
There are literally hundreds of CMS applications that drive websites, some of the most popular being WordPress, Joomla, Drupal, OpenCart, PrestaShop, Magento, SMF and so on.