Content management is a phrase to describe how you store, update and present the text, images, video and documents on you website. Often the system allows you to change the menu structure, where things appear on the screen and control who changes what, when and how.
There is a good trend towards separation of information and presentation of information which really makes communicating ideas simpler and faster. Once presentation of information is structured, such as how many columns of text, how to photos fit in, what fonts and sizes are to be used, and what type of information goes where, the adding of information itself becomes much easier.
This removes the need to use website designers to update or even add content, they are used where they can be of most benefit, in the design of how information is presented. This saves your business money, time and improves the delivery of information to your customers. It means information can be presented according to the device or medium you are using. Which makes it more transferable, dynamic and ultimately more useful to your business operations.
There are of course many flavours of content management systems available for use both open source and proprietary. We generally use one of three open source solutions, WordPress, Drupal and Joomla although there are more we can offer such as SimpleCMS, MediaWiki and many others.