The pillars of web development technologies are HyperText Markup Language (HTML), Cascading Style Sheets (CSS), JavaScript (JS), and web application programming interfaces (APIs).

HTML is the language that is used to structure websites, with HTML you can insert text, images, videos, create different sections for your website, create links to other sites, and more. CSS is a styling language that helps you edit how your HTML elements look, how they are displayed and how they are arranged on your screen. It is also what makes user interfaces responsive for different devices like mobile, tablet, laptop, desktop, and others by providing APIs which dynamically resize your HTML elements based on the width and height of the screen a specific user has. JavaScript is a programming language that makes your HTML elements dynamic, it allows for things like complex animations, dynamic formatting of elements depending on given inputs, state management within your application, much more utility thanks to its programmability, and more. HTML, CSS, and JavaScript are the only 3 technologies that browsers understand, the rest of the technologies mentioned in this specialization end up compiling to an optimized HTML, CSS, and JS bundle which the browser can process and interpret.

The best place to learn the basics of web development in my opinion is freeCodeCamp where you can do the lessons in the first two sections named “Responsive Web Design” and “JavaScript Algorithms and Data Structures”. It says that each section takes about 300 hours each, but usually, you can do it in much less since it’s a conservative estimate. After you’ve gone through these two sections and made the initial projects that are required to fulfill them you can move on to learning React. Another great place to learn is the Mozilla developer documentation where you can learn everything about HTML, CSS, JS, Web APIs and their specifications, protocols like HTTP and other web technologies.