What is a CMS?
The short answer: In the context of building a website CMS is an acronym for Content Management System.
The long answer: A website Content Management System (CMS) is a set of tools designed to allow users with little knowledge of website technology or markup languages to create and manage content quickly and easily.
A Content Management System separates the content of a web site, the user added material such as text and images, from the framework of linking pages together and controlling how the pages appear.
The goal of a Content Management System is to make a site easier to maintain than would be the case if it was built exclusively out of hand coded html pages or just using a simple html editor.
The main features of a Content Management System
While the Content Management System is a power tool in the sense that it allows designers and developers a way to create websites, it is also a powerful tool in that once the modules are installed and the theme is created, someone does not need a lot of technology understanding to update and add content.
Once content is separated from the visual presentation of a site, it usually becomes much easier and quicker to edit and manipulate. Standard templates can be automatically applied to new and existing content, allowing the appearance of all content to be changed from one central place. If you do your homework ahead of time, and have some content ready to add to your site, you can have a website up and running in a very short period of time.
Scalable feature sets are implemented through plug-ins or modules that are developed independently of the Content Management System. Additional features can be easily installed to extend functionality of the site without having to do a major rebuild.
With a content management system, the software that creates and manages the website is installed on the web server, not on your local desktop. You can add content quickly and easily from any location having internet access simply by using a web browser.
The biggest disadvantage of a CMS
Many sites primarily use common templates for design, typically a 2 or 3 column design with boxes placed in various positions to accommodate the content.
While the use of automated templates is listed as a major advantage of CMS, many people argue that being confined to using templates for design limits flexibility and uniqueness of design. This is quite subjective.
How to chose a CMS
Answering that question is the primary purpose of this site. There are well over 300 CMS (content management systems) out there. The Wikipedia page of free and open-source software lists over a hundred.
There is no such thing as "the best CMS." Anyone who starts telling you which CMS is the best, without first qualifying the context of their comments, is simply selling their services.