improve description for content management systems category

- https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2984

README.md

@@ -666,7 +666,7 @@ Software for submission of [abstracts](https://en.wikipedia.org/wiki/Abstract_ma
 
 **[`^        back to top        ^`](#)**
 
-CMS are a practical way to setup a website with many features. CMS often come with third party plugins, themes and functionality that is easy to add and customize to your needs.
+[Content Management Systems](https://en.wikipedia.org/wiki/Content_management_system) offer a practical way to setup a website with many features, using third party plugins, themes and functionality that are easy to add and customize.
 
 _Related: [Blogging Platforms](#blogging-platforms), [Static Site Generators](#static-site-generators)_