Poetry is the most complex textual form because it uses a specific macro language.
Analysis of a poem implies for the reader, the intelligent reader (who are able to read between the lines), to understand why, for which reasons, somebody has used language in that way and to explain why the poet conveys the message. A symbol is something concrete that relates something else. A simile is generally used to better describe something, to provide a description and to help the reader to imagine the situation. Personification attributes human qualities to something there isn't human. Generally all figures of speech create a more vivid meaning. Irony is used to convey a situation less dramatic. It expresses something, stating it opposite. Imagery is an uncountable noun, and it implies all the words in the poetry, namely it is the sum of the imagines. Allusion makes an indirect reference to something. Alliteration is the repetition of the same consonant sound. Assonance is the repetition of the same vowel sound and it is used to create a more fluent message, to suggested what has been told and to stick in the reader's mind that imagine.
Literature started as an oral form., it was no written. How could people remember? Poets had to use language in a way people could remember. Bards and minstrels had to make what they composed memorable, therefore they use language in a way similar to today's songs: they use a lot of alliterations, rhymes, assonances, incremental repetitions and refrains. So people could remember. Oral composition were handed over from generation to generation. Language was concrete, simple and the topics of such literature were strictly connected to their lives.
What was the most popular form of such literature? It was ballad. The attitude of dancing and singing entered with the entry of Christianity. Christianity had such a diffusion because it promised salvation, it gives a reason to live.
On Sunday, the Day of the Sun, people went to church to celebrate the mass. People sang in Latin because Latin was the language of religion, the original language of the church. But most people were illiterate, they weren't able to write and to read. So, what gave meaning to their praying? Their faith did. Their effort gained in meaning and in value. They believed in what they sang and they learn by heart all the prayers.
Literature is the expression of the community.
People had community festivals in which they sang and danced and where people from all classes could meet.