If there ever is or was something during your education that you didn't quite understand, know that you were given a bad explanation. Having been taught even by MIT grads and given bad explanations, I can assure you that bad explanations are all too common in academia. The identifying mark of a bad explanation is that it makes it difficult to extrapolate. Consider a bad explanation of what a dictionary is: "A dictionary defines words". It makes some sense. If you want to find the meaning of a word, you can use a dictionary. But try to extrapolate. Why are there more than one definitions of words? Why don't dictionary makers just define one word in a single way to avoid confusion? Because the explanation of the dictionary was bad, it is difficult to answer these questions. The correct explanation of a dictionary is "A dictionary RECORDS how words are used". With this explanation it is possible to extrapolate. Like why are there multiple meanings of the same words? Because people use the same words in more than one way. And so the dictionary records all the ways the words are used by the speakers. This is very common in academia. You're often given a bad explanation. But because the wrongness is usually subtle, you can't immediately tell that it's bad. But know that if you cannot answer new questions using the explanation you were given that you were given a bad explanation. Like if you can't extrapolate why we can't make RAM as fast as Cache or make Cache much bigger than a few MBs, you were given bad explanations of RAM and Cache.