The language module or language faculty is a hypothetical structure in the human brain which is thought to contain innate capacities for language, originally posited by Noam Chomsky. There is ongoing research into brain modularity in the fields of cognitive science and neuroscience, although the current idea is much weaker than what was proposed by Chomsky and Jerry Fodor in the 1980s. In today's terminology, 'modularity' refers to specialisation: language processing is specialised in the brain to the extent that it occurs partially in different areas than other types of information processing such as visual input. The current view is, then, that language is neither compartmentalised nor based on general principles of processing (as proposed by George Lakoff). It is modular to the extent that it constitutes a specific cognitive skill or area in cognition.
Language faculty in the context of Universal grammar
Universal grammar (UG), in modern linguistics, is the theory of the innate biological component of the language faculty, usually credited to Noam Chomsky. The basic postulate of UG is that there are innate constraints on what the grammar of a possible human language could be. When linguistic stimuli are received in the course of language acquisition, children then adopt specific syntactic rules that conform to UG. The advocates of this theory emphasize and partially rely on the poverty of the stimulus (POS) argument and the existence of some universal properties of natural human languages. However, the latter has not been firmly established.
Other linguists have opposed that notion, arguing that languages are so diverse that the postulated universality is rare. The theory of universal grammar remains a subject of debate among linguists.
View the full Wikipedia page for Universal grammar