The document discusses two models that are useful for understanding how marketing communications work: the macro model and micro model. The macro model focuses on the communication process between a sender, message, media, and receiver. It also describes the major functions of encoding, decoding, response, and feedback. The micro model focuses on consumer responses and discusses the hierarchy-of-effects model whereby marketing moves consumers through the steps of awareness, knowledge, liking, preference, conviction, and ultimately purchase. The document notes that getting a consumer through all these steps has only a 0.0001% probability, highlighting the challenge of marketing communications.