In most lectures, it's just the lecturer talking and the students listening and taking notes, but it does depend on the lecturer. I had a French grammar lecture this year where we had to do exercises and then the lecturer just randomly picked on people to give the answers- and there were about 120 of us! I also had a couple of lectures that felt more like seminars because they were either option modules that weren't particularly popular or compulsory modules that just didn't have that many students. Seminars follow on from the lectures, but you're in groups of about 10-15 and you're expected to discuss the points raised.
But to add to what some other people said, what the hell is the point of paying 3k a year to sleep or listen to your ipod?!! You might as well not bother going to a lecture if you're going to do that- it's a waste of time if you're going to have to listen to it later anyway, not to mention that some lecturers won't let you record them and even if they do, you might not get very good quality. If I saw someone doing that in a lecture, I'd think they were rude, lazy and wasting their time by being at uni, so yes, I'd say it would create a bad impression!