What is a Content Management System ( CMS )
In the context of websites, a Content Management System is a <dynamic website> that itself contains the means to generate and edit content.
The idea behind a CMS
A CMS has two faces: pages dedicated to displaying content, and pages dedicated to creating and managing it. The content itself can be anything from articles, images, videos, comments and talkbacks regarding existing content — all depending on what each CMS offers.
In a standard site, whenever you need to add or change content, you create the new content on your own local machine and then upload it to the remote server. With a CMS, you only upload the core files of the CMS once, when you set up the site. All additions and changes to content are made by visiting certain pages of the site in your regular browser. This allows you to concentrate on your content instead of the code that will display it.
This mechanism allows many users to collaborate in creating content, though it's as commonly used by a single website master. Usually all actions associated with the site—like watching content, commenting, creating new content, and changing the site's feel and look—are restricted by roles or permissions, and the site administrator (who installed the CMS in the first place) can assign and revoke these at will.
What the casual site visitor sees is usually called "the front-end", whereas the special administration pages are called "back-end".
Look and feel
In most CMSs, the look and feel of the website can be changed by using "themes" or "skins". Such a CMS will have a back-end page or number of pages dedicated to managing themes. Once you add the theme files to your server, the theme will become available on those pages. By choosing it, all existing and new content will be displayed according to the new scheme. Separating content from looks gives you flexibility as your site grows and changes.
Types of CMS
There are specialized CMSs for <blogs>, portals, message boards, <shopping cart> solutions, online courses, and many more.
Many excellent CMSs are available as free <Open Source> projects. Most of them rely on a combination of <PHP> and <MySQL>, though you need to know neither in order to work with a CMS once it's installed.
For almost every CMS you'll find an active Internet community that revolves around improving the CMS, designing new functions for it (usually called "plugins" or "modules"), and creating a wide selection of themes. Today more than ever, CMSs allow you to build complicated, highly-interactive dynamic sites without needing to master a programming language.