HTML stands for HyperText Markup Language. It is the standard markup language used to create and structure content on the web. HTML elements are the building blocks of web pages, defining headings, paragraphs, links, images, and more.
CSS stands for Cascading Style Sheets. It is a stylesheet language used to describe the presentation of a document written in HTML. CSS controls the layout, colors, fonts, spacing, and overall visual appearance of web pages.
JavaScript is a versatile, high-level programming language primarily used to add interactivity and dynamic behavior to websites. It runs in the browser and can manipulate the DOM, handle events, make network requests, and much more. It is an essential technology of the modern web alongside HTML and CSS.
Responsive design is an approach to web design that ensures web pages render well on a variety of devices and screen sizes. It uses flexible grids, flexible images, and CSS media queries to adapt the layout to the viewing environment, providing an optimal user experience on desktops, tablets, and mobile phones.