THEME, PURPOSE, MEANING
This is important. All writing has a purpose - this is why it was written! But, oh dear - so many students write their essays without having this idea at the centre of their mind. Whenever you analyse a text for your course - play, poem, story or non-fiction text - it is vital that you do not begin your analysis until you have worked out its author's main purpose(s) - the theme(s) of the text.
Here is a useful definition of theme: 'The theme of a piece of fiction is its controlling idea or its central insight. It is the unifying generalization about life stated or implied by the story. To derive the theme of a story, we must ask what its central purpose is: what view of life it supports or what insight into life it reveals.' (Laurence Perrine; Story and Structure, 1959).
In all essays, your main idea will be connected in some way with the writer's purposes and your analysis will be to show how the writer has chosen language (and in non-fiction and media texts, also presentational features) that will appeal to a certain kind of reader - the audience for the text - in order to achieve whatever purpose is intended.
Stories - as well as poems and plays - are an entertaining form of writing. The purposes behind a literary text of this kind is called its theme. Such texts have been designed, unlike say a text that simply gives instruction or information, to involve the reader deeply and emotionally; they are written so that the reader will relate closely to the text's main character or the idea explored in an absorbing, enjoyable way.
Remember, though, that few authors write solely to entertain - most write to persuade. Many texts have a moral purpose. This means that their story - poem or play - becomes a vehicle for the author to put over a persuasive message concerning some aspect of society.
Clearly, we can only very rarely actually ask an author about his or her purpose, intention or reason for his or her text, so you will need to develop insights into what the author might have meant to achieve. You do this by interpreting the text. Sometimes what a text means is blindingly obvious ('Fish and Chips - Only £2.99 today!'); sometimes it might seem all but hidden ('Tyger! Tyger! Burning bright in the forest of the night' - just what are those 'forests of the night', for goodness sakes!). This latter kind of text is where subtle interpretation of various possible layers of meaning is called for.
In English essays, what gains most marks is when you show you have understood the text's various layers of meaning. These exist within the more subtle and complex texts you study in class and in the exam. You will need also to identify how particular language choices made by an author act to shape and add layers of meaning. Only by doing this will you come to recognise the writer's true purpose or theme.
You should also recognise that for the more subtle texts you will study, it is impossible to know exactly what a writer meant to be understood by the text and that no single interpretation is ever really possible. This is because not every reader will 'read' or interpret a text in quite the same way. So when you discuss meaning, consider alternative ways of interpreting the text.