HTML (HyperText Markup Language) is the standard markup language used to create web pages. It provides the structure and content of websites by using a system of tags and elements that tell web browsers how to display text, images, links, and other content.
CSS (Cascading Style Sheets) is used to style and layout web pages — for example, to alter the font, color, size, and spacing of your content, split it into multiple columns, or add animations and other decorative features.
JavaScript is a programming language that enables interactive web pages. It is an essential part of web applications for any web browser. JavaScript can update and change both HTML and CSS, can calculate, manipulate and validate data.
Expand/collapse widgets (accordions) help reduce clutter on a page by allowing users to reveal content only when they need it. They improve user experience by making information more organized, scannable, and accessible on devices with limited screen space.