"Understanding" is a word that is hard to define. I'll put it this way: when you feel like you've finally understood something, you possess understanding (some of the time, at least). This is not the same as merely knowing that something. It is not merely a feeling, but the feeling is there when you have understanding.

It follows from this "definition" that computers/algorithms/whatever do not possess understanding. They do not understand things like we do; they merely use grammatical rules and a set of axioms to derive new propositions from a set of initial statements.

If you want to test this assumption yourself, picture yourself being given a list of instructions to follow. Now picture that these instructions, if performed, do something, but you cannot understand what it is that they're doing. You most clearly do not possess any understanding in this scenario. This is exactly how computers work