A Content Management System (CMS) enables site administrators to update the website via an Admin Panel. It wasn't so long ago that, for every change no matter how tiny, you needed to call your web developer (which may be why they were called "webmasters"). Now, many if not most sites have an Admin Panel where you can plug in your changes.
At the early stages of a web project, CMS-related decisions need to be made. Firstly, do you need one? For a site that won't change much, a "static" build is fine (just contact us if you need anything).
Most clients want the ability to make their own changes. The ease and elegance of your finished CMS depends on how much development effort was put into it. A site that allows you a great deal of flexibility and ease-of-use will cost more than one that only allows you to change a few things — but that cost may well be worth it! Both people and search engines love to see fresh content on your website.
The other decision is what CMS product to utilize. We typically work with ExpressionEngine or WordPress, but we can do others (like Drupal) if there's a preference. Once the Web Design phase is (mostly) complete, we install the chosen CMS and program it in accordance with the site's design and logic. Then we teach the client how to use it.
We have built countless, easy-to-use CMS sites for our clients. Check out our Portfolio for details.