To put it plainly I sat through many lectures I didn't understand. I've sat through several courses where I didn't understand anything the whole term. Sometimes I was very interested but I didn't use very good learning strategies. I could have raised my hand in class or gone to the instructor's office hours but I didn't. I tried the library with no success. It's easy to be smart in retrospect and see what I could have done.

With advanced technology perhaps we can do a lot better. To learn you need to proceed from what you understand and assimilate new ideas in that context. By asking questions you can build the necessary bridge. Moreover the questions and answers will form a repository that will grow over time with new additions.

Please try the Ask a Question link. I do not know who is asking the questions, so you can ask anything without fear of embarrassment. The site is solely to help you learn.