How to understand HTTPS / SSL?

I deployed a python server a few weeks ago, but for that I had to use nginx.

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And following the tutorial, I talked about enabling https / ssl.

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Okay, I did that.

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Now I am studying Nginx to better understand how it works, but in the Ningx course (Linux Academy) it doesn’t cover things so much about https / ssl, it only covers things like enabling using lets encrypt and certbot.

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But I want to understand how it works behind the scenes.

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What readings are recommended for this?

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PS: all tutorials on how to enable https with nginx use certbot with lets encrypt.