Answers to tasks: What are the main functions of language?

What's the origin and the meaning of the word grammar?
The term "grammar" can also describe the linguistic behavior of groups of speakers and writers rather than individuals. Differences in scales are important to this sense of the word: for example, the term "English grammar" could refer to the whole of English grammar (that is, to the grammar of all the speakers of the language), in which case the term encompasses a great deal of variation. At a smaller scale, it may refer only to what is shared among the grammars of all or most English speakers (such as subject–verb–object word order in simple declarative sentences). At the smallest scale, this sense of "grammar" can describe the conventions of just one relatively well-defined form of English (such as standard English for a region).
What is the subject of grammar? Give its two interpretations.
The word "grammar" derives from Greek and means "art of letters" (gramma = letter). The term "grammar" is used in two meanings. On the one hand, in its wide sense, the term refers to the theory which is constructed by the linguist to describe the speaker's linguistic competence. On the other hand, in its narrow sense, the term "grammar" refers to the study of morphology and syntax
What's the difference between Descriptive and Prescriptive Grammars?
There is a descriptive grammar of language that does not tell you how you should speak or what rules you should know in order to speak. It only describes the rules that are already known. the prescriptive grammar tells what rules you should know to speak the standard language.
What's the aim of Teaching Grammar?
a teaching grammar which is used to learn another language or dialect. Teaching grammars are used in schools to fulfill language requirements.
What's the essence of Chomskian Transformational-Generative Grammar?
Chomsky believed, that by a limited number of kernel sentences and a set of transformational rules one can generate (create) innumerable syntactic combinations.Chomsky and his followers formulated transformational rules with the help of which a sentence with a given grammatical structure can be transformed into a sentence with a different grammatical structure but the same essential meaning. For instance, the sentence "John saw Mary", which is in the active voice, can be transformed into the passive construction "Mary was seen by John."