For most of the web applications, the choice of frontend tech stack remains similar. Modern web applications are based on HTML, CSS, JavaScript, TypeScript, or frameworks based on JS, like React, Vue,Angular and Express.

HTML

HTML (Hypertext Markup Language) defines the basic layout and structure of your pages. For example, the sections, bulleted points, and tables are created using HTML tags..

CSS

All the styling that's applied to the web pages comes from CSS — for example, the Blue theme of the Jsxcode pages.

JavaScript

The dynamic elements of the page come from the JavaScript code written by developers.

For example, what happens when you hover your mouse over an image, or when you click on a submit, like, or comment button is decided by JavaScript events in the code.

HOW DO HTML, CSS AND JAVASCRIPT FIT TOGETHER?
To make this easy to understand, I'm going to refer to these three web languages as different aspects of the human body.
Please click here
The Website as a Human Body

I Did a Video Presentation From A-Z about Front-End
The Secret of Complete Responsive Web Design

There are many other frameworks and libraries - like Bootstrap, React, Vue,Angular, and jQuery - that are built on JavaScript and provide additional functionalities and common use cases, making a developer's life much easier.