Collapsible Accordion

HTML stands for Hyper Text Markup Language. A markup language is a set of markup tags.HTML documents contain HTML tags and plain textHTML documents are also called web pages. HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items.
JavaScript is the programming language of the Web. JavaScript is the most popular programming language in the world. All modern HTML pages are using JavaScript. The HTML DOM (the Document Object Model) is the official W3C standard for accessing HTML elements. JavaScript can manipulate the DOM (change HTML contents). It is the language for HTML, for the Web, for computers, servers, laptops, tablets, smart phones, and more.

CSS

CSS stands for Cascading Style Sheets. Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g., fonts, colors, spacing) to Web documents. Styles define how to display HTML elements. External Style Sheets can save a lot of work. External Style Sheets are stored in CSS files.