With regard to the Russian case system, what cases are included when "the oblique cases" are referred to?

Question

I was in the midst of trying to educate myself on "collective numerals" when I came across this:

To say that the usage of двое, трое, etc., is limited to the nominative case would be incorrect. Yet, there is no doubt that in many instances the oblique cases of два, три, четыре, etc., are definitely preferred.

From "Table of Collective Numerals," RussianLearn.com.

I am having difficulty understanding the excerpt above and part of the stumbling block is that I am really just guessing at what is meant by "oblique cases." I might still have difficulty understanding the passage, but attempts to comprehend it are stymied by the fact that my notion of "oblique cases" is somewhat nebulous. Are oblique cases all cases but the nominative? Or are they a subset of cases beyond the nominative? And, if so, which ones? I've tried searching for this information online, but have not seen anything yet that addresses this question.

Answer 1

Answering your question: in Russian, all cases except the nominative are considered oblique (косвенные падежи). The "direct case", as opposed to oblique ones, is the one you put the subject into.

In other languages, cases other than nominative can serve as subjects. Those usually include the vocative and sometimes the accusative in nominative-accusative languages (compare English colloquial "me and Bill went to the store").

The excerpt you're quoting is a somewhat clumsy way of saying something among those lines:

Many say that you can use the collective numerals двое, трое etc only in nominative, and with all other cases you should use the cardinal numerals два, три etc. This is not exactly right. You can put the collective numerals like двое, трое into all cases. However, with cases other than nominative, the usage of cardinal numerals like два, три is indeed preferred.