JavaScript is a high level, often just in time compiled language that conforms to the ECMAScript standard. It has dynamic typing, prototype based object orientation, and first class functions. It is multi paradigm, supporting event driven, functional, and imperative programming styles. It has application programming interfaces (APIs) for working with text, dates, regular expressions, standard data structures, and the Document Object Model (DOM).
Web Development and Content Management Systems Rely on PhP, HTML, Javascript, MySQL and CSS to function. These are the most common languages in modern Web Development.
The frontend is the content management application. It enables writers, editors, and project managers to work seamlessly without the need to code. The backend is the content delivery application, which is used for publishing and displaying the content in various formats based on the CMS.
Instead of building your own system for creating web pages, storing images, and other functions, the content management system handles all that basic infrastructure stuff for you so that you can focus on more forward facing parts of your website.