So, what I am wondering about is what I should look up to study the following. From my understanding, there is a limited number of ways languages are implemented. That is, there is a set of abstract constructs which languages utilize. For example, declensions, tenses, moods, etc. Those are then either implemented in a language in a certain way or thrown out altogether. In the latter case, the language somehow makes do without it.
What I would like to study is this grammar in the general sense, without necessarily being attached to a particular language. However, I then plan to use those things in the study of some languages. To give you an idea, after this study, I would know exactly what Acusativus, sg. means and so on. I actually already do know what it means because we have six noun declensions in Russian. But two of them all but disappeared, when compared to, say, eight original declensions found in vedic Sanskrit. Hence, some of them I am not necessarily familiar with. The goal would be to study this abstract grammar first, know what these concepts are and then be able to use them in the study of languages.
If you know any books on this or at least what the area of study is called, I am all-ears.