The document discusses the role, purpose, and identification of the main idea in written texts. It explains that the main idea is the central and most important point that a text is about. Supporting details provide additional information and examples to explain the main idea. The document provides examples of stated main ideas, which are directly stated, and implied main ideas, which must be inferred. It also offers strategies for identifying the main idea, including considering the topic, what the author wants the reader to know, and using a T-note format to organize main ideas and supporting details.