Grammar, usually taken to consist of the rules of correct syntactic and semantic usage, becomes, in [philosopher Ludwig] Wittgenstein’s hands, the wider—and more elusive—network of rules which determine what linguistic move is allowed as making sense, and what isn’t. This notion replaces the stricter and purer logic, which played such an essential role [in his first book] Tractatus in providing a scaffolding for language and the world. Indeed, “Essence is expressed in grammar … Grammar tells what kind of object anything is. (Theology as grammar)” (PI [Philosophical Investigations] 371, 373). The “rules” of grammar are not mere technical instructions from on-high for correct usage; rather, they express the norms for meaningful language. Contrary to empirical statements, rules of grammar describe how we use words in order to both justify and criticize our particular utterances. But as opposed to grammar-book rules, they are not idealized as an external system to be conformed to. Moreover, they are not appealed to explicitly in any formulation, but are used in cases of philosophical perplexity to clarify where language misleads us into false illusions.
Grammar is not abstract, it is situated within the regular activity with which language-games are interwoven: “… the word ‘language-game’ is used here to emphasize the fact that the speaking of language is part of an activity, or of a form of life” (PI 23).
— “Ludwig Wittgenstein,”