Development of grammars
Grammars evolve through usage and human population separations. With the advent of written representations, formal rules about language usage tend to appear also. Formal grammars are codifications of usage that are developed by observation. As the rules become established and developed, the prescriptive concept of grammatical correctness can arise. This often creates a gulf between contemporary usage and that which is accepted as correct. Linguists normally consider that prescriptive grammars do not have any justification beyond their authors' aesthetic tastes. However, prescriptions are considered in sociolinguistics as part of the explanation for why some people say "I didn't do nothing", some say "I didn't do anything", and some say one or the other depending on social context.
The formal study of grammar is an important part of education from a young age through advanced learning, though the rules taught in schools are not a "grammar" in the sense most linguists use the term, as they are often prescriptive rather than descriptive.
Constructed languages, (also called planned languages or conlangs) are more common in the modern day. Many have been designed to aid human communication (such as Esperanto or the intercultural, highly logic-compatible artificial language Lojban) or created as part of a work of fiction (such as the Klingon language and Elvish languages). Each of these artificial languages has its own grammar.
It is erronously believed that analytic languages have simpler grammar than synthetic languages. Analytic languages use syntax to convey information that is encoded via inflection in synthetic languages. In other words, word order is not significant and morphology is highly significant in a purely synthetic language, whereas morphology is not significant and syntax is highly significant in an analytic language. Chinese and Afrikaans, for example, are highly analytic and meaning is therefore very context dependent. (Both do have some inflections, and had more in the past; thus, they are becoming even less synthetic and more "purely" analytic over time.) Latin, which is highly synthetic, uses affixes and inflections to convey the same information that Chinese does with syntax. Because Latin words are quite (though not completely) self-contained, an intelligible Latin sentence can be made from elements placed in largely arbitrary order. Latin has a complex affixation and a simple syntax, while Chinese has the opposite.