I read an answer here that said a description says HOW something is while an explanation entails WHY it is that way. If so then how do we determine when something has been explained (if it can be)? For example, I understand that when it rains the ground becomes wet. Why? I don't know the chemistry behind it but water is wet and covers the ground. But some could ask WHY is it wet and not something else to which many would respond "It just is". Is "It just is" the real explanation? Is the real explanation to everything "It is what it is", even though we may not know what IT is?

Very interesting! It is not easy in the abstract to form a sharp distinction between an explanation and a description. Presumably, every explanation involves some description (you are describing the cause of an event, for example), and any description of a thing could probably be used as part of an explanation (e.g. at a minimum, the description "I am reading AskPhilosophers" could be the answer to this request: "What are you doing right now?" and so on). What counts as an explanation may depend on the relevant inquiry. There are fairly restrictive accounts of what counts as a good explanation in the natural sciences (Hempel's nomological explanations) but then there are what Hempel called explanation sketches that are more loose. "It is wet" could be a sufficient explanation as to why you are not wearing a specific coat, though it would not get at why the coat got wet or why you prefer a dry coat. Your reference to "It is what it is" sort of explanation suggests a category of BASIC explanations...