Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.
The HyperText Markup Language, or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript.
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.
A content management system (CMS) is a computer software used to manage the creation and modification of digital content (content management). A CMS is typically used for enterprise content management (ECM) and web content management (WCM). ECM typically supports multiple users in a collaborative environment by integrating document management, digital asset management, and record retention.