This paper is primarily concerned with explaining some basic concepts in modern linguistics, and clarifying fundamental misconceptions which people sometimes have about, these concepts. After a short introduction on Chomskys key contributions to the study of language and the study of mind, in part 2 we have argued that the most fundamental reason for studying language - and for Chomsky, the most compelling reason - is that languageis a mirror of mind. In our study three interrelated theories about language have been analysed: Theory of Language Structure, Theory of Language Acquisition and Theory of Language use. We have tried to show the attempts which have existed in understanding the general principles of organization in both language and uses of language. In Part 3 we have argued that notions such as "correctness" , "acceptability", "pragmatic anomaly" and "semantic ill-formedness" should not be confused with descriptive notion of "grammaticality". In Part 4 we have argued that why language acquisition is a creative and rule-governed activity; and the task of the linguist devising a grammar of a language is to hypothesize a finite set of phonological, syntactic, morphological and semantic rules which will generate the infinite set of well-formed sentences in language. In Part 5 we have noted that the linguist should collect a set of relevant data about well-formedness and structure, and try to devise a hypothesis about the principles governing the language.