The theme is the main idea that the writer of the poem wishes to convey to his/her readers. It is the main idea around which the poem is focused.
Briefly speaking, the theme of the poem is the attitude of the poet toward the subject of the poem. For instance, the subject is about love and you have to find out from the poem what he or she thinks about love and write it down in a complete sentence. Eg. Love makes us miserable. The sentence expressing theme must be generalized. In other words, it should be applicable to almost everyone.
A message the story expresses
Its just homework from school and the teacher said find out what it means and write an essay on it we had a poem given to us and we have to find the theme of the poem