"A content management system, or CMS, is a system used to organize and facilitate collaborative creation of documents and other content. A CMS is frequently a web application used for managing websites and web content, though in many cases, content management systems require special client software for editing and constructing articles. The market for content management systems remains fragmented, with many open-source and proprietary solutions available." -- Wikipedia
Basically, a CMS brings together many different website publishing/authoring technologies together into a single database management system. Many websites are primarily "static"--that is, most of their content has to be updated manually, by updating the code on individual pages and then uploading them. Some websites are partly CMS-based; any website which includes a Message Board, Guestbook, Events Calendar, Mailing List or Searchable Database falls into this category. A CMS basically acts as a single engine controlling several or all of the above features, and can also include additional features such as member profiles, photo galleries, and so on.
The advantages of installing a CMS are obvious--it allows organizations to update their own website information without having to pay a third-party web developer to do so, which can save money in the long run. They also allow website content to be organized, displayed and linked to in multiple ways, making them ideal for integration with newer "Web 2.0" technologies like RSS feeds and social networks like Facebook, Twitter, and so on.
The disadvantages are that it can take a considerable amount of work to properly install and configure a CMS, which can result in a higher up-front cost; there are some limitations on the layout and design style of CMS-based websites due to their modular/template-based nature; while they are usually simple for general members to utilize, there can be a significant learning curve for the primary website administrator; and the website hosting needs are usually greater than a static site (they usually require support of both PHP and MySQL databases; all of Brainwrap's hosting solutions support both). As a result of the above, a CMS is usually overkill for smaller or even many mid-sized websites.
Brainwrap will be happy to discuss your own website needs to help you decide whether you require a static site, a semi-interactive site, or a full content management system. Remember, you can always start out simple and build as your website--and your business--grows!