As mentioned above, websites are made by writing in the HTMl language, and the HTML language is made out of things called HTML tags. There are lots of different tags available for use.

If you sit down and study for a long time, maybe you could memorise all of them, but that's not very healthy. When you make your own website, you'll naturally gain an understanding of the tags.

There is no one website that uses all the HTML tags in the world out of necessity. Look up unfamiliar tags when you need them. That's the stance you should take when it comes to HTML.

Back in the day you might have bought a Big Book of HTML Tags, but these days you can just use websites like W3Schools or MDN Web Docs to help you.

Rather than memorising tags, ask yourself: What do I want to create? What tags will I need to use to achieve that goal?