HTML is a standardized hypertext markup language for viewing web pages in a browser. Web browsers receive an HTML document from the server via HTTP/HTTPS protocols or open it from a local disk, then interpret the code into an interface that will be displayed on the monitor screen

CSS is a formal language for describing the appearance of a document written using a markup language. Can also be applied to any XML documents, such as SVG or XUL.

JavaScript is a multi-paradigm programming language. Supports object-oriented, imperative and functional styles. It is an implementation of the ECMAScript specification. JavaScript is typically used as an embedded language for programmatically accessing application objects.