A sundial is a simple device used to tell time by using the position of the sun. It consists of a flat plate, called the dial, and a stick or gnomon that casts a shadow on the plate. As the sun moves across the sky, the shadow moves around the dial, indicating the time of day based on the angle of the sun. Sundials have been used for thousands of years, dating back to ancient civilizations like the Egyptians and Greeks. They are often found in gardens and parks as decorative elements, showcasing both their historical significance and the beauty of natural timekeeping.