Difference (other than version) between HTML & HTML5?

I want to start studying HTML + CSS, but I can’t seem to pin down which to learn. Basic HTML or HTML5. I know its a version difference, but if I learn HTML5, will that essentially teach me what I need to know from HTML?

Like, I know Python 3.6 and it gives me a general knowledge of Python 2.X but obviously there are differences. Same with CSS, do I go study basic CSS or go for CSS3 ?irs.gov

I don’t have a current use case/purpose to study either except that I want to learn it. Ideally, I’d learn enough to (way down the line) net me a remote working job, but that’s a far flung hope and I mostly just want to learn to learn. Sorry if this has been asked a ton, tried to find it but didn’t see anything.
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