When you start something new, all the symbols are "too close together" and it takes time and repetition to increase the "resolution" on that map so that you can put the symbols into position with more precision and not have them confused with one another. You don't yet have a good intuition for the significance of each symbol and it won't come from being told, because sources have biases - frequency over time and space is a much stronger signal. It's the same with connections between symbols.
Doing, rather than just reading, is important; you need to try and find that Goldilocks zone of growth, where if things are easier you're not learning but if they're harder you lose hope. Try something just beyond what you know how to do, page in new information on demand when you get stuck (from docs, people, source code, whatever it is).
Writing notes helps me personally creating the space for symbols and reminding myself of what I already heard about but I don't know that it's necessary for everyone, and I especially think I've found it more useful as I've gotten older (and know more stuff already). Sometimes when I learn something "new", I pin it close to a concept I already know, which dulls its novelty and I'm probably more inclined to forget it, until I'm reminded of it again. And this is down to that "creating mental space" idea again.
Repetition increases symbol salience, particularly when you're surprised by the divergence between what you thought something meant and what it actually means. The risk of simply reading, and not doing, is that you're not surprised often enough. Doing stuff keeps you honest.