Huge part of Framer is functional (you'll just call stuff with options), other than that, I can come up with this right now:
Arrays (and some of their built-in methods), for loops, basic functions, scoping, know what an event is, know what a callback function is; probably some debugging techniques.
Don't worry about Framer library being too difficult to learn—they have decent docs and great community of helpers here :)
Someone can extend this for Brain?
I think Framer would be a great playground for learning a very similar scripting language. The problem with the JS landscape these days is that there are too many tools and methods for beginners to know where to begin. Framer makes it easy to do 93.488% of front end work. Once you get your footing, moving on will likely be much easier. That's just my opinion after doing it the hard way.