HTML, CSS and JS
Without HTML you can't have anything. For something to appears on the browser, you will need him. He will give a semantic sense to the content wrapped in the code. HTML is one of the base pillars on which the internet is built.
CSS alone can't do anything but with HTML he can be powerful. You not will hack NASA, but you can disable all JS functionalities related to pointer events. With CSS you can change the appearance, the format of how content is displayed, add some logic interactions, animations and make the content even more attractive.
JS is powerful, you can make programs with it, you can track people's actions on the page, make interactions with complex logic, request, construct, send and display data. And all of this without the user knowing. But for the JS to interact with users, and display data for them in the browser, HTML is mandatory required and, to make this content attractive, CSS will be needed.
You just need for most of the cases the three pillars and even one of them can be optional (JS).