Sometimes it's hard for us developers who are too close to our subject to try to explain it to others. It helps to attempt to explain it to non-developer friends, practice analogies and see what seems to make sense to people. Also know your audience. Some folks will be tech-savvy others will be tech-phobic, you'll need at least two explanations. I teach a class "Build your own website using Wordpress" and I get many students who have never heard of Wordpress. I explain that Wordpress is simply a way for them to create a website without having to know coding languages. And once you explain what "content" is most of them seem to understand the idea of a CMS. Teaching the admin area of WP is different than explaining the concept. The admin area can be made simple if all you want to do us to use it simply. The trick is to teach all the ins and outs so that they can make their site their own. That's why I teach a 9 session class, and they always leave wanting more.