Different universities use different terminology for their teaching systems. For example, at Oxford a tutorial is the core teaching method, and involves one, two, and sometimes three undergraduates in discussion with a tutor, usually focused on an essay written by one or more of the undergraduates. At Cambridge, this is called a supervision. At other universities, a tutorial may be a larger group session with a tutor. Some other universities might call this a class or a seminar. Lectures are probably much the same at most universities, with an academic presenting material, often via powerpoint slides, over an hour or two to a large group of students.
A key difference between school and university is that, at university, the student is expected to do a lot of independent reading and, to an extent which varies from course to course and from place to place, to self-instruct with varying amounts of guidance from the academic staff. The university student's week tends to be less timetabled than it is for a pupil at school, and students have to get used to organising their work when not having contact with academic staff. Falling behind leads to needless stress and may impact performance, so keeping on top of the work is a thing worth doing. There is usually still plenty of time for socialising, playing sport, doing performance art, taking part in clubs etc.