It's hard to say whether it is a research-level question without seeing the question itself.
If you are working through an undergraduate textbook and it got you to wondering, odds are that this is more likely to be appropriate on CS.SE. If you are doing research on theoretical computer science (e.g., reading research papers published in peer-reviewed conferences, collaborating on a research project with an established researcher), it might be more appropriate on CSTheory.SE.
Given your comment that you are looking to "learn the basic ideas about his formalism, obviously not at research-level but in a more divulgative-fashion", that definitely sounds like a question for CS.SE. CSTheory.SE is for research-level questions about theoretical computer science.