My favorite (evidence backed) theory on how humans learn is Retrieval Practice.
https://www.learningscientists.org/blog/2024/3/7/how-does-retrieval-improve-new-learning

Humans don’t really learn when we download info into our brain, we learn when we expend effort to pull that info out. This has some big implications for designing collaborative tooling!

The “thing” that we learn most effectively is not knowledge as we typically think of it, it’s process. This should be intuitive, if we put into a bit of a more natural context. Imaging learning baking for a moment: Do you teach someone to bake a cake by spitting out a fact sheet of ingredients and having them memorize it? Or do you teach them the process?