There are 3 main subject groups. The VO, IV and UE. Every study program has all of them so let us get to understanding them a little more. One thing all these subjects have in common is, that we students have 5 chances to pass each of them before we cannot continue studying at this university anymore. But besides that, they are full of differences.
VO (Vorlesung), here we have the more theoretical aspect of the course, usually the professor or lecturer teaches us about the subject in a less interactive way, we can discuss and ask about the matter presented, and since classes are generally small compared to other universities, our lecturers always find enough time to answer all our questions.
Attendance is not mandatory for VO lectures, however for many subjects it is highly recommended. Especially at the beginning of the Bachelor, when you are just getting acclimated to Uni life, where everything is left up to you.
Once class is over, we have the “Schwammerl Antritt”, which just means the first exam date for each VO subject. Probably the best one for you if you attended class or have been studying along. These exams are almost always written, but some subjects may also have an oral examination as well.