Here are the simplified definitions of prose and poetry:
Prose--the ordinary, matter-of-fact, ordinary form of language
Poetry--the art of rhythmical composition for exciting pleasure by imaginative or elevated thoughts.
There are times when prose that contains elevated thoughts and a beauty of expression is referred to as being "poetry." Therefore, the division between the two is certainly mitigated at times by beautiful language or inspired thoughts.
While prose has as its definition, "written or spoken language in its ordinary form, without metrical structure," it certainly can share with poetry some poetic qualities such as lyricism and the use of literary devices such as metaphor, simile, symbolism, paradox, imagery, and so on.
For example F. Scott Fitzgerald, a writer of prose, is often described as a romantic lyricist because there are elements of Romanticism in his writing and the structure of his prose is so lyrical in nature at times with its balanced and poetic phrases and lilting sentence structure. Consider this passage from The Great Gatsby:
But his heart was in a constant, turbulent riot. The most grotesque and fantastic conceits haunted him in his bed at night. A universe of ineffable gaudiness spun itself out in his brain while the clock ticked on the wash-stand and the moon soaked with wet light his tangled clothes....For a while these reveries provided...a satisfactory hint of the unreality of reality, a promise that the rock of the world was founded securely on a fairy's wings. (Ch. 5)
So, while prose can often be poetic, poetry rarely is prosaic, although it can be rather mundane and matter-of-fact at times, as in some modern poems.
No poem in the traditional sense of ode, elegy, epic, sonnet, etc. can be judged as similar to prose. These formal forms have the restrictions of meter and rhyme and form. Appearance is very different as prose is composed of paragraphs and/or dialogue while poetry is arranged in verse and lines