Web development itself and how it is done has changed greatly over the years, but one thing has remained the same: web development is about creating applications which run in a web browser.
Some of those applications have most of their logic living on a web server which renders HTML, CSS, and JavaScript to create an application.
Other applications only utilize the server to create their initial state, download the logic to run the application, and then use the server only to retrieve and store data.
Regardless, though, of how web development is done, the basic technologies are the same: HTML, JavaScript, CSS—and a large amount of patience.
This is possible because the user interface of a web application is essentially HTML, CSS, and Javascript which can be generated by any programming language capable of generating text.
JavaScript is used to manipulate what is known as the DOM (Document Object Model), which is a representation of a webpage in the browser, to directly change the user interface displayed in the browser without directly creating new HTML or CSS code.