Using Math as an example; there are 50 or so different math courses, from "Early Math" to "Class 10 (Marathi)". I'm sure these course names make sense to some people, but many of them seem to be meaningless outside of a specific school system to which I'm not privy.
The lack of descriptions makes it difficult to figure out what to learn, without already knowing what you're about to learn.
A simple one-line description for each course, explaining why it contains the modules it does, would make it way easier for learners to focus on the right thing. This can be as simple as "This course contains all trig content seen in grade X in some US school system".
I used math as an example, but this applies equally well to every other course on the website.