There are three things to a web site:

• The colours and layout that appear on each page.
• The structure of how the pages link together.
• The data in each page; words, pictures, etc.

In old style web sites this information was contained within a set of files that each had all three types of information. Modern web pages don’t work like that. A modern web site separates each of these things separately. There are a number of reasons for doing this, the main reason is to allow a set of pages to have a common look and feel to them without the need for each individual page to be constructed exactly the same. In the individual page method it was almost impossible to make any changes.

 A content management system is software that allows you to create great pages without all of the complexity of thinking about the three layers. It also allows people to focus on the content that they want to publish without worrying about the whole site.

In the Joomla Content Management System (that this site uses) the colour and layout of the site is controlled with a template. The structure of where the pages appear are controlled by the use of Sections and Categories. The actual pages are created from information stored in the Sections, Categories and in Items that are added to the Categories. It sounds complicated but really it’s quite straightforward, creating an item is just like adding a file to a folder on a disk. The publisher of an item doesn’t need to worry about where the item will appear on the site or how it looks, because that’s what the Content Management Systems does.

The other great thing about a content management system is that once a structure is created people can be granted permission to add in items without the need for there to be a single web site administrator. They don’t need to worry about causing damage and the Web Site administrator can get on with doing something they are more interested in. 

More details of what a Content Management System I can be found here.