I often watch online courses and work-related videos, and I saw a blogger with a Mac screen split in two to view two programs at once, combine two processes, or watch an online lesson on one side while immediately applying it in practice on the other side. How can I set this up?

In essence, if the laptop is powerful, it shouldn’t be an issue. I’m not sure if this can be done in Mac's standard settings, but you can definitely achieve this with third-party software https://setapp.com/how-to/split-screen-on-mac-for-extra-productivity. I read positive feedback about Swish, and it’s supposed to be super easy to use; it should work fine for what you need. But if that doesn’t suit you, the article lists other methods, all of which seem quite decent.