HTML, CSS, JS
That's kinda the core, after that there are so many topics in web development that are neat but you may never see or use...
I'd take a look at getting that core down, then learn some git, pick a framework like React or Angular and make something with those.
C0D45946527dthese days "webdev" is so generic that it means nothing.
Learn the basics, vanilla JS, CSS3, HTML and then move into either react/angular/vue/svelte for the JS framework.
Pickup on Accessibility and UX and you'll be able to drive the conversation in a professional manner.
Then just build things and experiment.
Backend wise... you can use python, java, c#, php, nodeJs, or a number of other languages.
It really comes down to what you see as "webdev" and what you want to build as to where we can really point you.
Benutzername52827dSprinkle a little bit of sql knowledge to what the guys have already mentioned.
pxeger45125d> oop/strong typing language guy