Layout principles refer to the guidelines that help organize visual elements in a design. These principles include balance, contrast, alignment, repetition, and proximity. By applying these principles, designers can create a harmonious and effective composition that guides the viewer's eye and enhances understanding. Effective layout principles improve readability and user experience in various mediums, such as web design, print media, and advertising. For instance, using contrast can highlight important information, while alignment ensures that elements are visually connected. Overall, these principles are essential for creating clear and engaging designs.