An abstract noun is a word that refers to something that cannot be perceived by the senses. Abstract nouns often refer to ideas, emotions, or qualities. For example, the word "love" is an abstract noun because it refers to an emotion that cannot be seen, heard, or touched.
Concrete nouns are words that refer to something that can be perceived by the senses. Concrete nouns often refer to objects, people, or places. For example, the word "table" is a concrete noun because it refers to an object that can be seen and touched.
In the case of poem, song, and story, all of these words refer to abstract concepts. A poem is a piece of writing that expresses a thought or feeling, a song is a piece of music that is typically sung, and a story is a narrative that tells a sequence of events. None of these things can be perceived by the senses, so they are all abstract nouns.