HTML is an acronym for, hypertext markup language. Consists of elements that contain tags. This language is used for website creation. Each website page contains writing, images, and hyperlinks for navigation.

JavaScript is a object-oriented scripting language. It is designed primarily for adding interactivity to web pages and creating web applications.

CSS, short for cascading style sheets, it is used to add font, color, images, fine tuning positions, margins, and other look and feels of a webpage. CSS is used in conjunction with HTML although HTML offers inline styling, but CSS is easier to use and more clean.

For GitHub specifically ,it is a basic text editor attached to repositories. Often describes what the conjoining code does, modifications, uses, and proper steps on how to use it.