Explain Formal Language Grammar

A formal language grammar is a set of formation rules which explain which strings formed from the alphabet of a formal language are syntactically valid, in the language. A grammar just only addresses the location and manipulation of the strings of the language. It does not explain anything else regarding to a language, like its semantics.

Like proposed by Noam Chomsky, a grammar G contains the subsequent components:

a. A finite set N of non terminal symbols. 
b. A finite set Σ of terminal symbols that is disjoint from N. 
c. A finite set P of production rules, every rule of the form where * is the Kleene star operator and determines set union. That is, every production rule maps from one string of symbols to another, where the first string consists of at least one non terminal symbol. 
d. A distinguished non terminal symbol from set N which is the start symbol.