what is an overarching theme of a text? what is the difference between that and the Message the author is trying to get across

Although they can often overlap, overarching themes do not need to convey anything. Instead, they are common things that appear throughout a story. It may be a physical representation of an object being repeated, or it could be an idea or construct being repeated. This differs from the message because these do not outright convey meaning. They link together the whole story and often elude to the message.