Theme and topic are two terms that are usually considered to be the same by most people, but there are so many differences between the two. The theme of a particular literary piece simply refers to the overall interpretation or meaning that the whole of the literary piece wants to pass across to the reader.
A topic is a subject that reveals the exact information which a writer is trying to pass across. While themes are not usually included when writing, a lot of topics can be treated in a bid to explain a particular theme. A topic will inform a reader about what is expected to be learned at that particular time.
However, most people get to understand the information which a theme is trying to convey after they might have finished reading a literary work. A theme will answer the question as to why a particular literary piece has been written, while a topic will give you the whole information.