Based on Word Count
Novel (40,000 words or over): A fictitious prose narrative of book length, typically representing character and action with some degree of realism.
Novella (17,500 to 39,999 words): A short novel or long short story.
Novelette (7,500 to 17,499 words): A short novel, typically one that is light and romantic or sentimental in character.
Short Story (under 7,500 words) A story with a fully developed theme but shorter and less descriptive than a novel.
One Shots : (typically more than 1000 wards) A story that starts and ends in one chapter. There is no restriction of no. of characters.
Flash Fiction / Ficlet : (typically 1000 words) Fiction typically consisting of only a few hundred words.
Vignette : (typically 500-1000 words) : It focuses on a specific moment or scene or maybe thoughts of a character.
Drabble : (typically within 100 words) A drabble is a short work of fiction of ideally one hundred words in total. It is for testing the author's ability to express interesting and meaningful ideas in a confined space.
Poem: Piece of writing in which the expression of feelings and ideas is given intensity by particular attention to diction (sometimes involving rhyme), rhythm, and imagery.
Poetry : literary work in which the expression of feelings and ideas is given intensity by the use of distinctive style and rhythm; poems collectively or as a genre of literature.
Difference between poem and poetry (Poetry is a literary form, whereas a poem is a written piece of work. Poetry is an art form, whereas a poem is a composed work. He who composes poems occasionally cannot be called a poet but can be called a versifier. A poem is the fundamental unit of poetry.)