Ooh exciting! You will go to class in a video conference room or classroom. The rooms I have seen generally have two large flatscreen tvs - one will generally show content such as Powerpoints etc and the other will generally show the video conference itself. The video conference screen will display video feeds of each connected campus/location in smaller boxes down the side and the main image will show whoever is speaking. Your lecturer may be on your campus and the class shared with students on other campuses/locations. Or you lecturer may be on another campus or location. At a guess, class should run similar to normal lectures/tutorials, all depends on the class/lecturer.
Technology being what it is, always try to arrive early for a video conference class and be prepared for possible delays at the start of each class. The video conference software will dial in at the exact time it is supposed to start and hang up at the exact end time. I guess it depends on the size of the class and location etc but sometimes the door will be locked (if your lecturer is at a different location), someone from a previous video conference might have rearranged the furniture or someone might need to turn on the tvs or call for tech help if there are any problems.
All classes are compulsory. As far as I know there is no such thing as optional classes or lectures.