CMS, or content management systems allows people who don't know a whole lot about HTML and programming to be able to design websites with out having to first take a course in how to do it.
Why would people use it-CAUSE ITS EASY!!!! (and makes their lives a lot easier)
How does it work???-the pages are created by CMS software and edited by the author without changing the software. And page design is based on a template. The user just puts their own info in.