Design principles are a set of guidelines and best practices that inform the development of products, systems, or services. They are used to ensure that the end result is functional, user-friendly, aesthetically pleasing, and meets the needs of the target audience. Design principles often address factors such as usability, accessibility, simplicity, consistency, and visual appeal. They help designers make informed decisions throughout the design process, leading to more successful outcomes. Design principles can vary depending on the specific context and goals of the project but generally aim to create a cohesive and satisfying user experience.