'Theme' is a literary term used to convey the central idea or message in a literary text. The theme is not the same thing as the subject of the text. For example, the subject of the story "Chicken Little" is a paranoid little chicken, but the theme of that story could be fear or hysteria.
One of the key points in literary analysis when reading a poem or novel is to be able to identify what the theme is. Understanding the theme of text is important, because then the reader can make connections to what the author's purpose for writing the text may have been.
For example, in Macbeth by William Shakespeare, the central character Macbeth murders the king so that he may rule...
instead. A central theme of this play is ambition, because the Macbeth's thirst for power causes him to commit terrible acts. Athematic statement then describes how the theme relates to the specific text; for example: In the play Macbeth, unchecked ambition leads to dire consequences.