CMS or Content Management Systems are platforms one can use to build website. Familar brands of CMS are Joomla and Wordpress. It is much easier for a site owner to edit sites built on CMS. The sites have a way to login to the administrative area. Here the pages, called Articles, can be access and edited without the use of typical website editing software such as Dreamweaver. 

The Articles in a CMS website can be turned on and off as needed and even be set to be present for a defined period of time. Modules are available to "add-on" to the CMS website. The modules can be things like shopping carts, customized forms, etc.

Many of the websites I produce use the Joomla CMS platform. The website  is an excellent example of a Joomla-based website.