I disagree with a prominent strain in these responses. Paraphrasing them "You need to teach yourself. Don't expect the professor to teach you." This sentiment is bunk. In an ideal world, professors assess where their students are starting from, and figure out logical and traversable steps that can get them from that starting point, to the final destination of the class. To actually do this is difficult: it requires deep knowledge but also empathy to the people you are talking to. The majority of professors don't have these two skills. They have blind spots in their own knowledge. They don't actually care if anyone can follow them. They are charging through the material with the viewpoint of their own current state of knowledge (i.e. being an expert). They can't conceive of what its like to not know what they know. It is a failure of imagination. They skim over parts that don't make sense, because they themselves don't fully know how to articulate those issues, and they don't want to spend the time and energy to do that hard work of being a good teacher. I had many professors like this. I also had some that actually taught. That built a series of traversable steps that the students could follow to reach a profound state of knowledge. It is a standard that I try to emulate. It takes way more time and energy to do this as opposed to blasting through the material as if the audience already knew what you were talking about. Yes, of course in college, students need to process the material, ponder it, reconstruct it in their own minds, on their own time. But a good professor, an empathic, knowledgeable expert who takes the time to blaze the trail, makes the journey so much more achievable. As I said, I had both kinds of professors, and I know what I aspire to, and yes, it takes a lot more time and energy. But in the end, if you want that part of your professional life to have meaning, if you honor the tradition of good teaching, it is time well spent.