<p>the MWF is lecture and the M is discussion section. lecture will have all enrolled students (this is why the MWF times are the same all the way through when looking at a class) and the different CRNs correspond to different sections. it’s not always mandatory; maybe half of the classes i’ve had had mandatory sections. usually if it’s mandatory it is for a reason and vice versa, for example, right now i go to all of my linguistics sections because we have to turn in homework and take a weekly quiz, but i never go to my econ section because all my TA does is rehash lecture poorly so i have no real reason to go.</p>
<p>waitlist just means, the class is full so you get put on a list. if one person leaves, one person from the waitlist gets in. if 50 people leave, 50 people from the waitlist gets in.
so, it completely depends on how many people drop the class. i suggest you do go to the classes though, because they’ll usually tell you what the situation is, like “oh if you’re number 15 or less you’ll probably get in” or whatever. there are also PTA(permission to add) numbers that you can sometimes get from the professor, and they’ll usually address that issue during the first class as well.</p>