Prose refers to ordinary written or spoken language with regular or predictable grammatical structure as used by ordinary writers and speakers in everyday life. The word first appeared in written English in the 14th century, derived from an old French term, which in turn came from the Latin phrase prose ratio, meaning straightforward or direct speech. In regular usage, prose is counterpoised with the contrast-term poetry. Everyday speech and written works in science, philosophy, journalism, social sciences, business, government and law are generally written and spoken in prose.
To some extent, developments in modern language, linguistics and experimental usages by writers have rendered the very idea of prose less and less meaningful, even arguably obsolete, although it is still widely used and promoted in academic and pedagogical circles (notably by, teachers of English in K-12 education, and writers). They accept the dichotomy as expressed by a character in Molière's play Le Bourgeois gentilhomme where the character Monsieur Jourdain asked for something to be written in neither verse nor prose. In response, a philosopher replies: “There is no other way to express oneself than with prose or verse. . . Everything that is not prose is verse, and everything that is not verse is prose". ( "Le Bourgeois Gentilhomme". Act II. English translation at Project Gutenberg. Retrieved 11-7-2020.)
A century ago, the poet T.S. Eliot highlighted the paradoxical nature of the idea of prose when he remarked, “the distinction between verse and prose is clear; the distinction between poetry and prose is obscure.” Developments in modern poetry, since that time have served to highlight and reinforce Eliot’s point. Traditionally, the term prose referred to language lacking obvious meter or rhyme, but with developments in modern and contemporary poetry including free verse, prose poetry and concrete poetry and other new poetic directions, the original distinction of prose and poetry has far more limited significance. Prose is now seen by some as a position at one end of a continuum with poetry at the other end, although the many differing, even conflicting, perspectives on meter and rhyme in poetry render even this dichotomy somewhat threadbare. Rather than a continuum, the prose-poetry relation has more the character of a complex branching diagram, with new nodes added periodically. (For example, economic poetry. 
Because of its origins in Latin, distinctions between prose and poetry are universal to European languages, notably Germanic and Romance languages. The extent to which it applies to predominantly spoken languages, even those with strong lyrical tendencies, like Algonquin, Navaho or the many languages of the Indian subcontinent, is not completely clear.
For some writers, the noun poetry and the adjective poetic seem to refer primarily to creative uses of language; an idea that associates prose with ordinary, dull or unimaginative language use.
Perhaps the most fundamental distinction of various types of prose is the distinction between fiction and non-fiction. Fiction is written or spoken prose primarily concerned with story-telling that includes imagined or invented names, characters, places, events and scenes. Fiction can be divided many different ways. For example, distinguishing between novels and short stories, or by subject matter into such types as crime fiction, fan fiction, science fiction, spy fiction, romance literature and numerous other types. Non-fiction prose generally makes claims of presenting or describing what is real, notably real events and actual persons. Non-fiction is typically concerned with conveying accurate information. It is probably the larger and more varied category, at least in terms of subtypes, including current affairs, history and biography, scientific writing, journalism, and government and business communication all falling under that rubric.