There are a ton of tags. https://www.w3schools.com/tags/ref_byfunc.asp shows a good list of them.
From my limited knowledge, i would say 250 is a good estimate. The best thing about HTML is how easy it is. for example in one my lines of code i put:
<iframe src="enter basic sharable google drive url here" width="910px" height="700px" border="0" ></iframe>
the iframe tag makes a box that will display some item, usually a website of sorts. Or anything with a URL
src="" is what the source is. Anytime you will be pulling in outside information you will need to determine the src, or the source.
once you run that you quickly realize the box is to small, so we can add width inline with the code to change the width. Same with the height.
The easy part of HTML is all these things are usable with any other tags. You can change the border, the width, the height, all with the same modifiers.
so anytime you need to change the width, just add "width="200x". where x is what measurement you want, px for pixels, or % for a percent of the screen width.