Principle is a design and animation tool for creating interactive user interface prototypes with a focus on motion design. It allows designers to animate transitions, gestures, and interactions, helping to visualize the user experience before development. Principle supports an intuitive drag-and-drop interface, enabling designers to quickly build prototypes without coding. Its advanced animation features, such as timelines and ease functions, allow for smooth, realistic transitions. Principle is ideal for UI/UX designers looking to communicate interactions and animations effectively to developers and stakeholders.