Diffraction is a phenomenon that occurs when waves encounter an obstacle or a slit that is comparable in size to their wavelength, causing them to spread out. To better understand this concept, it's recommended to ask specific questions or refer to particular sections of the Princeton Review AP Physics B book. Engaging with online resources, such as Wikipedia, can also provide clearer explanations and examples. Providing context or links to specific content can facilitate more targeted assistance from others. Clarifying your questions will enhance the likelihood of receiving helpful responses.