Perhaps, in the past, we could get away with rote learning, memorisation and vomiting everything onto the page. But with the modernisation of education, even standardised tests and assessments have moved towards a more creative approach of asking questions. They may present you with something you’ve never seen before and expect you to answer appropriately through analysis and inference, using the available information. It will undoubtedly be related to something you’ve encountered before and the basic concepts in the textbook, but the link may not be immediately apparent. Training yourself to see such patterns and applications will be of immense help.
Usually, the answer keys / mark schemes of practice papers are much clearer, more direct and succinct than the lengthy explanations in textbooks and lecture notes. I have a habit of taking these down, especially for the commonly asked questions (like gel electrophoresis and the steps of the adaptive immune system for A-Level Biology) and adding them to my notes. Using these summarised explanations and processes to revise can save lots of time too!