The document discusses the three stages of Understanding by Design (UBD) which are identifying desired results, determining acceptable evidence, and planning learning experiences and instruction. It focuses on the first stage of identifying desired results and the importance of using essential questions which should be open-ended, non-judgmental, thought-provoking, and succinct. Essential questions address important recurring questions in life, point to core ideas in a subject, and help engage students through curiosity, problem-solving and multidisciplinary investigations. Examples of essential questions are provided for different subject areas.