Most of the notes I take are about things I plan to use somehow. This is for 'random' reading, not in a school context.
For example, I might find some tool to better monitor Kubernetes clusters, and I'll copy-paste that into a document about that topic.
Or I might find some cool feature in an obscure programming language, and decide I may want to implement that one day. I have a whole bunch of documents for that topic.
I don't really write things down if I don't think I can take action on them at some point. Maybe I should though, just to remember better.
If I'm not on my PC, I'll often put the notes on my task list, and organize them later.