Look.
there are mainly 2 kind of websites
1) static
2) dynamic

I'm not going full technical. i'll try to explain as simple as possible.

let's discuss static websites first.

static websites are websites with constant pages and content. you make static websites when you know that these contents will never going to change.
for example, a blog. you write a blog and just upload it, there is nothing to be controlled using an automated script. right..?
yes, you need to update your blog time to time, but you can do it manually. these websites can be build only using HTML and CSS and basic JS.
these kind of websites are hosted on server where HTML pages are served directly.
like www.000webhost.com without any charges, but you do need to pay for the domain name.

now let's discuss dynamic websites.

dynamic websites are websites with content wich may vary time to time like facebook. it's not static, when someone shares something on their wall you should see that content too. meaning have to build something that shows you the content which can be anything and posted by anyone.
and to build these websites, we need three things, server (to serve APIs also called back-end), user interface (website design a user interacts with also called front-end) and admin panel (a special front end designed for admin of that website to control the settings)..

servers can be coded in
node.js
python
Java
ruby
or etc... (I'm not gonna name them all)

user interfaces and admin interface can be coded in
javascript
Java servlet

to code front-end in JavaScript we need JS frameworks like VUE.JS, react.js, and etc...
and if you're using Java servlets then you'll only need plain JS or TS(type script, somewhat upgraded version of JS but not JS)

coming to the server part.
your server needs to expose some APIs to the open world in order to save data into DB and get data from database..
like if someone wants to post a picture then you'll code an POST API which takes a picture from user and saves that picture in the database or local repo (depends on your website behaviour).
but at same time you need to display that uploaded picture onto someone's profile then you'll have to expost a GET API to get all or selected pics from the database and shows it to the user.

and while coding the front end you need to consume these APIs and automate your front-end JS to automatically get pictures wherever someone posts a picture.. there are many methods to do that like pub/sub, oraclize services, events and etc.

and admin interface is almost like user interface but with different functionality, suppose you want certain user to stop posting pictures or you wanna block someone entirely, then you need an admin panel to do that instead of updating the database manually for every user.


-CODING IS DONE HERE-

after the coding part is done you need a public server to serve your website on an IP address so people can use it..
servers like AWS, GCP, azure and etc.

upload your server code on any server and note down that server's IP address, let's say it is "192.168.1.1"

now every API calls will be coming from or going to that IP address so you need update your API calling from local address to that IP address in user and admin interface (from "http://localhost/someAPI" to "http://192.198.1.1/someAPI") ..
and upload these interface on a server as well, it can be the same server or a different server, it doesn't really matter if you're learning.

after you've uploaded the code onto a server you need buy a domain name like "www.something.com" and map that domain name to the IP address of your front-end server's IP address using nginx or any other services you like, and upload a SSL certificate to enable "https" in your website (HTTPS protocol uses a secure port to communicate and ensures your website's security).


and that's basically it.